Photographic products, processes and compositions

ABSTRACT

Photographic films and particularly film units for performing diffusion transfer processes, are disclosed which may be processed outside of a camera. A light-absorbing reagent is employed to prevent postexposure fogging by actinic light passing through a transparent face of the film unit. After a suitable period, the light-absorbing reagent is rendered ineffective to prevent viewing an image through said transparent face. In a preferred embodiment, the image is viewed against a lightreflecting material such as a white pigment, said lightreflecting material and said light-absorbing material being employed in combination to provide desired protection against said postexposure fogging. Particularly useful light-absorbing materials are dyes which are light absorbing at a pH at which image formation is effected and nonlight-absorbing at a subsequently attained pH. Other light-absorbing reagents including dyes which are selectively mordanted to render them ineffective to prevent viewing transfer images visible against a light-reflecting material. The final image may be dye or silver. Suitable image-forming reagents include dye developers, color couplers, coupling dyes, etc.

United States Patent Land [ 1 Mar. 7, 1972 [54] PHOTOGRAPHIC PRODUCTS,

PROCESSES AND COMPOSITIONS [72] Inventor:

Related US. Application Data [63] Continuation-irI-part of Ser. No. 786,352, Dec. 23, 1968, Continuation-impart of Ser. No. 43,782, June 5, I970. abandoned.

[52] US. ..............96/3, 96/29 D, 96/84 R Primary ExaminerNorman G. Torchin Assistant Examiner-Alfonso T. Suro Pico AnomeyBrown & Mikulka and Stanley H. Mervis [5 7] ABSTRACT Photographic films and particularly film units for performing diffusion transfer processes, are disclosed which may be processed outside of a camera. A light-absorbing reagent is employed to prevent postexposure fogging by actinic light passing through a transparent face of the film unit. After a suitable period, the light-absorbing reagent is rendered ineffective to prevent viewing an image through said transparent face. In a preferred embodiment, the image is viewed against a light-reflecting material such as a white pigment, said lightreflecting material and said light-absorbing material being employed in combination to provide desired protection against said postexposure fogging. Particularly useful light-absorbing materials are dyes which are light absorbing at a pH at which image formation is effected and nonlight-absorbing at a subsequently attained pH. Other light-absorbing reagents including dyes which are selectively mordanted to render them ineffective to prevent viewing transfer images visible against a light-reflecting material. The final image may be dye or silver. Suitable image-forming reagents include dye developers, color couplers, coupling dyes, etc.

134 Claims, 18 Drawing Figures OPAOUE suPPoRT DYE DEVELOPER LAYER LVER HALlDE EMULSION OPNOUE PROCESSING FLUID RECEIVING LAYER SPACER LAYER RIC AcIo LAYER LAYER 8U P PORT DEVE LOPE R LAYER 8| LVER LAYER OF PROCESSlNG -RECElVlNG LAYER PACER LAYER YMERIC MID LAYER SUPPORT E SUPPORT DEVELOPER LAYER SILVER HALIE EMULSIN LECTING LAYER 51 Int. Cl .503, 5/54, 603C 7/00, G030 1/34 [58] Field ofsetll'ch ..96/3, 29 D, 84 R [56] Relerences Cited UNITED STATES PATENTS 2,983,606 5/1961 Rogers ..96/3 3,148,06l 9/1964 Haas ...96/3 3,345,163 10/1967 Land et al ..96/3 3,351,470 ll/1967 MCCune ...96/3 3,362,819 H1968 Land ....96/3 3,415,644 12/1968 Land ....96/3 3,455,686 7/l969 Farney et al.. ..96/3

STAGE A! Imme EXPOSURE DIRECTION STAGE BI PRocEsINe AMBIENT LIGHT STABE c [76 FINISHED PRlNT L AY ER TRANSFER IMAGE LAYE R ACID LAYER NT SUPPORT VlEWlNG DIRECTION IAIENIEDMIR 7 1972 SHEET (31 0F 11 OPAQUE SU PPORT DYE DEVELOPER LAYER ILVER HALIDE EMULSION OPAQUE PROCESSING FLUID MAGE RECEIVING LAYER SPACER LAYER STAGE A2 IMAGING I l r I l r I I r POLYMERIC ACID LAYER TRANSPARENT LAYER EXPOSURE DIRECTION RAND E R T E C E VI 0 VI E Am A M T L MP R VF G U mmm m PP IR WEMT P ODSE Y N U LNUVI EA 3 AA C m D M M WU EQMS AE W A M P Y L P R 00 FIS T m i I m m m a m m B I m &

AMBIENT LIGHT M E R m m n M M m RI R m L R L "R E H Y H F A P N A RL L U I T L R W N W m E AMA D s D V R I E E L Ll C T I VT w m s n A m E TEI R A E V CRN E P Q0 L Y A F. P E O R SPACER LAYER I I I I 1 lz STAGE C FINISHED PRINT Ejwam MM VIEWING DIRECTION and 2V. AT RNEYS FIGI PATENTEDMAR 7l972 3,647,437

sum near 11 INVENTOR. EDWIN H. LAND BY 6mm MW and M 1. 772M042 AT OHNEYS FATENTEDMAR 7:972 3,647.43?

SHEEI 03M 11 EDWIN H. LAND BY EJww n and 01nd 6221 1 5 M TORNEYS PAIENTEDMIR 7:9?2 3,647,437

sum nuur n TRANSPARENT SUPPORT POLYMERIC ACID LAYER ,"SPACER LAYER IMAGE-RECEIVING LAYER EXPOSURE )SILVER HALIDE EMULSION DYE DEVELOPER LAYER T "*OPAQUE SUPPORT I/OPAQUE SUPPORT DYE DEVELOPER LAYER /SILVER HALIDE EMULSION COLORLESS LAYER CONTAINING GTICAL FILTER AGENT PRECURSOR PKSMENTED PROCESSING COMPOSITION IMAGERECEIVING LAYER -SPACER LAYER --POLYMERIC ACID LAYER ,-ZI\TRANSPARENT SUPPORT INVENTOR. EDWIN H. LAND BY EXPOSURE DIRECTION 6 772,5 g

ORNEYS PAIENIEDIIAR 7:912 3.647.437

sum nsqr 11 REV A V fil oPAeuE suPPoRT I2- A I n I a l XWDYE oEvELoPER LAYER l4 --S|LVER HALIDE EMULSION -PIGMENTED PROCESSING (XJMPOSITION L coLoRLEss LAYERICONTAINING OPTICAL FILTER AGENT PRECURSOR |ai /L--IMAGERECEIVING LAYER 320 I 20 ----sPAcER LAYER TRANSPARENT SUPPORT EXPOSURE DIRECTION FIG.7

OPAQUE SUPPORT ""DYE DEVELOPER LAYER SILVER HALIDE EMULSION OPAQUE PROCESSING COMPOSITION PREFORMED PIGMENTED LAYER "IMAGE-RECEIVING LAYER SPACER LAYER POLYMERIC ACID TRANSPARENT SUPPORT EXPOSURE DIRECTION INVENTOR. F I 8 EDWIN H. LAND EWWM wrwl

" 5!. W A TORNEYS PATENIEDIIAP. (I972 3,647,437

sum usnr 11 -0PAQUE SUPPORT POLYMERIC ACID LAYER SPACER LAYER DYE DEVELOPER LAYER i SILVER HALIDE EMULSION OPAQUE PROCESSING FLUID I/IMAGE-REcEMNG LAYER 30c I TRANSPARENT SUPPORT EXPOSURE SURFACE FIG. 9

OPAQUE SUPPORT SILVER HALIDE EMULSION -OPAQUE PROCESSING COMPOSITION SID/ER RECEPTIVE LAYER I32 PACER LAYER Emc ACID LAYER -TRANSPARENT SUPPORT EXPOSURE DIRECTION ,I/-TRANSPARENT SUPPORT 230 E 1 2' i coLoRLEss LAYER CONTAINING ALKALI- AcT|vATEo oPTIcAL FILTER AGENT |4 }/SILVER HALIDE EMULSION IE? '3 T "M--'OPAQUE PROCESSING COMPOSITION I204 TIMING LAYER 232 22 IWPOLYMERIC ACID LAYER 2 TRANSPARENT suPPoRT INVENTOR. EDWIN H. LAND fi/wum and m amxi e6" H M A TORNE YS PATENIEDHAR 7 1972 SIIEEI 070? 11 I POLYMERIC ACID LAYER kTIMING LAYER OPAQUE PROCESSING COMPOSITION I SI LVER HALIDE EMULSION C(LORLESS LAYER COIITAINING ALKALI- ACTIVATED OPTICAL FILTER AGENT SILVER RECEPTIVE STRATUM EXPOSURE umcc'nofl FIG. I2

EXPOSURE DIRECTION --ADDITIVE COLOR SCREEN TRANSPARENT SUPPORT TRANSPARENT SUPPORT Call-LESS LAYER CGVTAINING ALKALI- ACTIVATED OPTICAL FILTER AGENT LLSILVER mum: EMULSION OPAQUE moczssms COMPOSITION SILVER RECEPTIVE STRATUM NTAINING BLEACHABLE DYE "POLYMERIC ACID LAYER wcwmq omscnou TRANSPARENT LAYER INVENTOR. EDWIN H. LAND 3mm Mm 2? fl. M

AT RNEYS OPTICAL REFLECTlON DENSITY 9 1y a OPTICAL REFLECTION DENSITY 9 N b 0 PATENTED 7 I9 2 3, 647. 437

SHEET DBDF 11 WAVELENGTH IN NANOMETERS saoado4zoa4oaeo4eosooszos4oseosaosoosaosq 9gg gg9m WAVELENGTH IN NANOMETERS EDWIN H. LAND FIG. I5

PATENTEDMAR "/1912 3, 7, 7

SHEET USUF 11 DENSITY OPTICAL REFLECTION O Q N 9 WAVE LE NGTH IN NANOM ETERS FIG. I6

INVENTOR. EDWIN H. LAND B i I fi/IMML Mill M 51. AT ORNEYS PATENTEDMAF. 7 I972 SHEET 10 0F 11 TIME, MINUTES FIG. I?

INVENTOR EDW|N H. LAND fi/ww n, and m and ,ilg 1'1. W TORNE YS PHOTOGRAI'HIC PRODUCTS, PROCESSES AND COMPOSITIONS This application is in part a continuation of copending application Ser. No. 786,352 filed Dec. 23, I968, (now abandoned) and in part a continuation of copending application Ser. No. 43,782 filed June 5, I970 (now abandoned).

This invention is concerned with photography and, more particularly, with photographic processes which are conducted outside of a camera and wherein undesired post-imaging fog is prevented by a light-absorbing reagent retained within the ultimate photograph, and with photographic products useful in performing such processes.

A number of photographic processes by which images may be developed and viewed within seconds or minutes after exposure have been proposed. Such processes generally employ a processing composition which is suitably distributed between two sheetlike elements, the desired image being carried by one of said sheetlike elements. The resulting images may be in black and white, e.g., in silver, or in one or more colors. Processing may be conducted in or outside of a camera. The most useful of such processes are the diffusion transfer processes which have been proposed for forming silver or dye images, and several of these processes have been commercialized. Such processes have in common the feature that the final image is a function of the formation of an imagewise distribution of an image-providing reagent and the diffusion transfer of said distribution to or from the stratum carrying the final image, whether positive or negative. It has also been proposed to form the final desired image in the photosensitive stratum per se by monobath processing to obtain a negative image or by so-called direct positive processing to obtain a positive image, employing processing techniques and physical film structures similar to those found useful in diffusion transfer processing. This invention is directed to providing techniques and film structures by which photographic processes, such as those noted above, may be performed, at least in part, outside ofa camera.

The primary objects of this invention are to provide photo graphic products particularly adapted for use in instances where at least a portion of the process is performed under conditions which would ordinarily result in postexposure fogging of the photosensitive material, and more particularly for use in diffusion transfer processes performed, at least in part, outside of the light-protective confines of a camera. A further object of this invention is to provide photographic products and processes wherein a light-absorbing reagent is employed to protect a photosensitive material against postexposure fogging, during at least the early stage of image formation, by light passing through a transparent element, said light-absorbing reagent being subsequently rendered ineffective to prevent viewing said image through said transparent element. An additional object of this invention is to provide diffusion transfer processes and products employing dyes which are light absorbing at a pH at which image formation is effected and nonlight-absorbing at a subsequently attained pI-I. Still another object of this invention is to provide photographic diffusion transfer processes and products wherein a light-reflecting material and a light-absorbing material are employed in combination to provide protection against postexposure fogging by light transmitted through a transparent element of the film unit, said light-absorbing material being rendered ineffective to prevent viewing the final image through said transparent element and against said light-reflecting material. Yet another object of this invention is to provide difi'usion transfer processes and products wherein a light-absorbing material is initially so positioned as not to interfere with photoexposure but is so positioned and/or constituted as to provide protection against postexposure fogging. A further object of this invention is to provide photographic products having the aforesaid characteristics wherein the photosensitive material is exposed through a transparent element, and distribution of a processing composition provides a laminate including said photosensitive material, said transparent element and an i age-carrying layer, and the image formed in said image-car rylng layer is viewed through said transparent element, the laminate being maintained as an integral entity after the process has been completed.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the product possessing the features, properties and the relation of components and the process involving the several steps and the relation and order of one or more of such steps with respect to each of the others which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings wherein:

FIG. I is a diagrammatic enlarged cross-sectional view of a film unit embodying the invention, illustrating the arrangement of layers during the three illustrated stages of a monochrome diffusion transfer process, i.e., exposure, processing and final image;

FIG. 2 is a perspective view of a photographic film unit embodying the invention;

FIG. 3 is a diagrammatic enlarged cross-sectional view of the film unit of FIG. 2, along section line 3-3, illustrating the association of elements during the exposure stage of a diffusion transfer process, for the production of a multicolor transfer image according to the invention, the thickness of the various materials being exaggerated;

FIG. 4 is a diagrammatic, further enlarged cross-sectional view of the film unit of FIGS. 2 and 3, along section lines 4-4, further illustrating, in detail, the arrangement of layers comprising the photosensitive laminate during the exposure stage of the transfer process;

FIG. 5 is a diagrammatic, enlarged cross-sectional view of the film unit of FIG. 1 exposed in a different manner;

FIGS. 6, 7, 8, 9 and I8 are diagrammatic, enlarged crosssectional views of additional dye developer film units, embodying this invention, during the exposure stage;

FIG. 10 is a diagrammatic, enlarged cross-sectional view of a film unit for forming a silver transfer image and embodying this invention;

FIG. 11 is a diagrammatic, enlarged cross-sectional view of a film unit for developing a negative silver image by monobath processing and embodying this invention;

FIG. 11 is a diagrammatic, enlarged cross-sectional view of a film unit for obtaining an additive color image and embodying this invention;

FIG. I3 is a diagrammatic, enlarged cross-sectional view of a film unit for obtaining a dye image by the silver dye bleach process and embodying this invention;

FIGS. I4, l5 and I6 are each graphic illustrations of the spectral absorption characteristics of individual pI-I-sensitive dye filter agents employed in the practice of the present invention graphically denoting the spectral absorption/optical density relationship of the agents at specified intervals during performance of a photographic diffusion transfer process of the invention; and

FIG. I7 is a graphic illustration of the optical density/unit processing time relationship of the filter agents of FIGS I4, IS and 16, at their respective M wherein Curve A denotes the optical/densitylunit processing time relationship of the filter agent of FIG. 14 Curve B denotes the relationship with respect to the filter agent of FIG. I5 and Curve C denotes the relationship with respect to the agent of FIG. 16.

As indicated above, this invention is primarily directed to photographic processes wherein the desired image is obtained by processing an exposed photosensitive material, preferably silver halide, with a processing composition distributed between two sheetlike elements, one of said elements including said photosensitive material. The processing composition is so applied and confined wifliin and between the two sheetlike elements as not to contact or wet outer surfaces of the superposed elements, thus providing a film unit or film packet whose external surfaces are dry. The processing composition may be viscous or nonviscous, and preferably is distributed from a single-use rupturable container; such pressure rupturable processing containers are frequently referred to as pods. The final image may be black and white, monochrome or multicolor and either negative or positive with respect to the photographed subject. The present invention is especially, if not uniquely, adapted for facilitating processing outside of a camera film units which are maintained as an integral laminate after processing. the desired image being viewed through one face of said laminate.

ln diffusion transfer embodiments of this invention the diffusible image-providing substance may be a complete dye or a dye intermediate, e.g., a color coupler. The preferred embodiments of this invention use a dye developer, that is, a compound which is both a silver halide developing agent and a dye. As disclosed in U.S. Pat. No. 2,983,606, issued May 9, 1961 to Howard 0. Rogers, a photosensitive element containing a dye developer and a silver halide emulsion may be exposed and wetted by a liquid processing composition, for example, by immersion, coating, spraying, flowing, etc., in the dark, and the exposed photosensitive element superposed prior to, during, or after wetting, on a sheetlike support element which may be utilized as an image-receiving element. In a preferred embodiment, the liquid processing composition is applied to the photosensitive element in a substantially uniform layer as the photosensitive element is brought into superposed relationship with the image-receiving layer. The liquid processing composition, positioned intermediate the photosensitive element and the image-receiving layer, permeates the emulsion to initiate development of the latent image contained therein. The dye developer is immobilized or precipitated in exposed areas as a consequence of the development of the latent image. This immobilization is apparently, at least in part, due to a change in the solubility characteristics of the dye developer upon oxidation and especially as regards its solubility in alkaline solutions. It may also be due in part to a tanning effect on the emulsion by oxidized developing agent, and in part to a localized exhaustion of alkali as a result of development. in unexposed and partially exposed areas of the emulsion, the dye developer is unreacted and diffusible and thus provides an imagewise distribution of unoxidized dye developer, diffusible in the liquid processing composition, as a function of the point-to-point degree of exposure of the silver halide emulsion. At least part of this imagewise distribution of unoxidized dye developer is transferred, by imbibition, to a superposed image-receiving layer or element, said transfer substantially excluding oxidized dye developer. The image-receiving layer receives a depthwise dif fusion, from the developed emulsion, of unoxidized dye developer without appreciably disturbing the imagewise distribution thereof to provide a reversed or positive color image of the developed image. The image-receiving element may contain agents adapted to mordant or otherwise fix the diffused, unoxidized dye developer. 1f the color of the transferred dye developer is afiected by changes in the pH of the image receiving element, this pI-l may be adjusted in accordance with welLknown techniques to provide a pH affording the desired color. In a preferred embodiment of said U.S. Pat. No. 2,983,606 and in the commercial applications thereof, the desired positive image is revealed by separating the imagereceiving layer from the photosensitive element at the end ofa suitable imbibition period. Alternatively, as also disclosed in said U.S. Pat. No. 2,983,606, the image-receiving layer need not be separated from its superposed contact with the photosensitive element, subsequent to transfer image formation, if the support for the image-receiving layer, as well as any other layers intermediate said support and image-receiving layer, is transparent and a processing composition containing a substance, e.g., a white pigment, effective to mask the developed silver halide emulsion or emulsions is applied between the image-receiving layer and said silver halide emulsion or emulsions.

Dye developers, as noted above, are compounds which contain, in the same molecule, both the chromophoric system of a dye and also a silver halide developing function. By a silver halide developing function is meant a grouping adapted to develop exposed silver halide. A preferred silver halide development function is a hydroquinonyl group. Other suitable developing functions include orthodihydroxyphenyl and orthoand para amino substituted hydroxyphenyl groups. In general, the development function includes a benzenoid developing function, that is, an aromatic developing group which forms quinonoid or quinone substances when oxidized.

Multicolor images may be obtained using color image-forming components such as, for example, dye developers, in diffusion transfer processes by several techniques. One such technique contemplates obtaining multicolor transfer images utilizing dye developers by employment of an integral multilayer photosensitive element, such as is disclosed in the aforementioned U.S. Pat. No. 2,983,606, and particularly with reference to FIG. 9 of the patents drawing, and also in U.S. Pat. No. 3,345,163 issued Oct. 3, 1967 to Edwin H. Land and Howard G. Rogers, wherein at least two selectively sensitized photosensitive strata, superposed on a single support, are processed, simultaneously and without separation, with a single common image-receiving layer. A suitable arrangement of this type comprises a support carrying a red-sensitive silver halide emulsion stratum, a green-sensitive silver halide emulsion stratum and a blue-sensitive silver halide emulsion stratum, said emulsions having associated therewith, respectively, for example, a cyan dye developer, a magenta dye developer and a yellow dye developer. The dye developer may be utilized in the silver halide emulsion stratum, for example, in the form of particles, or it may be disposed in a stratum behind the appropriate silver halide emulsion strata. Each set of silver halide emulsion and associated dye developer strata are disclosed to be optionally separated from other sets by suitable interlayers, for example, by a layer or stratum of gelatin or polyvinyl alcohol. In certain instances, it may be desirable to incorporate a yellow filter in front of the green-sensitive emulsion and such yellow filter may be incorporated in an interlayer. However, where desirable, a yellow dye developer of the appropriate spectral characteristics and present in a state capable of functioning as a yellow filter may be so employed and a separate yellow filter omitted.

The dye developers are preferably selected for their ability to provide colors that are useful in carrying out subtractive color photography, that is, the previously mentioned cyan, magenta and yellow. The dye developers employed may be incorporated in the respective silver halide emulsion or, in the preferred embodiment, in a separate layer behind the respective silver halide emulsion. Specifically, the dye developer may, for example, be in a coating or layer behind the respective silver halide emulsion and such a layer of dye developer may be applied by use of a coating solution containing the respective dye developer distributed, in a concentration calculated to give the desired coverage of dye developer per unit area, in a film-forming natural, or synthetic, polymer, for example, gelatin, polyvinyl alcohol, and the like, adapted to be permeated by the chosen diflusion transfer fluid processing composition.

As examples of materials for use as the image-receiving layer, mention may be made of solution dyeable polymers such as nylons as, for example, N-methoxymethyl polyhexamethylene adiparnide; partially hydrolyzed polyvinyl acetate; polyvinyl alcohol with or without plasticizers; cellulose acetate with filler as, for example, one-half cellulose acetate and one-half oleic acid; gelatin; and other materials of a similar nature. Preferred materials comprise polyvinyl alcohol or gelatin containing a dye mordant such as poly-4-vinylpyridine, as disclosed in U.S. Pat. No. 3,148,061, issued Sept. 8, 1964.

As disclosed in the previously cited patents, the liquid processing composition referred to for effecting multicolor diffusion transfer processes comprises at least an aqueous solution of an alkaline material, for example, diethylamine, sodium hydroxide or sodium carbonate and the like, and preferably possessing a pH in excess of l2, and most preferably includes a viscosity-increasing compound constituting a film-forming material of the type which, when the composition is spread and dried, forms a relatively firm and relatively stable film. The preferred film-forming materials disclosed comprise high molecular weight polymers such as polymeric, watersoluble ethers which are inert to an alkaline solution such as, for example, a hydroxyethyl cellulose or sodium carboxymethyl cellulose Additionally. film-forming materials or thickening agents whose ability to increase viscosity is substantially unaffected if left in solution for a long period of time are also disclosed to be capable of utilization. As stated, the film-forming material is preferably contained in the processing composition in such suitable quantities as to impart to the composition a viscosity in excess of 100 c.p.s. at a temperature of approximately 24 C. and preferably in the order of 100,000 c.p.s. to 200,000 c.p.s. at that temperature.

Difiusion transfer processes which have been commercialized for camera use originally required a dark chamber within the camera structure wherein the requisite imbibition and diffusion transfer could occur with little or no danger of further exposure. Subsequent commercial embodiments have permitted the film unit to be removed from the camera (thereby eliminating the dark chamber and reducing the size and weight of the camera) without fogging the developing photosensitive material by use of opaque supports to protect against light incident thereon; fogging by internal reflection within a layer of such film units, if a problem. could be controlled, cg, by incorporation of a small quantity of carbon black in the processing fluid and/or a small quantity ofa white pigment, e.g., titanium dioxide, in appropriate layer or layers of the imagc-receiving element, as disclosed in US. Pat. No. 3,35 l ,470 issued Nov. 7, 1967 to William J. McCune, Jr.

in the last-noted embodiments, the image-receiving element had to be separated from the processed photosensitive element in order to view the transfer image otherwise hidden from view by the opaque supports.

A marked reduction in the amount of required materials constituting the film pack or roll, is possible if the superposed photosensitive and image-receiving layers are maintained as a laminate after formation of the desired transfer image. Such a structure, however, requires that the support for the imagereceiving layer be transparent, rather than opaque, so that the transfer image may be viewed without separating the film lamination. This invention is primarily directed to facilitating the processing of such film units outside of a camera without fogging of the photosensitive material as a consequence of light incident upon said transparent support. In its preferred embodiments, this invention is especially directed to diffusion transfer processes providing a finished print comprising a laminate containing a visible transfer image and one or more developed photosensitive, e.g., silver halide, strata separated from the stratum containing the desired visible image by appropriate masking means, preferably a reflecting layer comprising a white pigment, e.g., titanium dioxide.

U.S. Pat. Nos. 3,415,644, 3,415,645 and 3415,646, all issued Dec. 10, i968 in the name of Edwin H. Land, disclose and claim photographic products and processes wherein a photosensitive element an an image-receiving element are maintained in fixed relationship prior to exposure, and this relationship is maintained as a laminate after processing and image formation. In these processes, the final image is viewed through a transparent (support) element against a reflecting, i.e., white background. In a particularly useful embodiment, photoexposure is made through said transparent element and application of the processing composition provides a layer of light-reflecting material to provide a white background. The light-reflecting material (referred to in said patents and applications as an "opacifying agent") is preferably titanium dioxide, and it also performs an opacifying function. i.e., it is effective to mask the developed silver halide emulsions so that the transfer image may be viewed without interference therefrom, and it also helps to protect the photoexposed silver halide emulsions from postexposure fogging by light passing through said transparent layer if the photoexposed film unit is removed from the camera before image formation is completed. The present invention is directed to improvements in the processes and products disclosed in the said patents and is particularly directed to providing light-absorbing materials effective to permit performing said processes outside of the camera in which photoexposure is effected. For convenience, the specifications of the said patents and applications are hereby specifically incorporated herein.

In accordance with this invention, a light-absorbing material or reagent, preferably a dye. is provided so positioned and/or constituted as not to interfere with photoexposure but so positioned between the photoexposed silver halide emulsions and the transparent support during processing after photoexposure as to absorb light which otherwise might fog the photoexposed emulsions. Furthermore, the light-absorbing material is so positioned and/or constituted after processing as not to interfere with viewing the desired image shortly after said image has been formed. In the preferred embodiments, the light absorbing material, also sometimes referred to herein as an optical filter agent, is initially contained in the processing composition together with a light-reflecting material, e.g., titanium dioxide.

The concentration of indicator dye is selected to provide the optical transmission density required, in combination with other layers intermediate the silver halide emulsion layer(s) and the incident radiation, to prevent nonimagewise exposure, i.e., fogging, by incident actinic light during the performance of the particular photographic process. it has been found, by interposing neutral density (carbon containing) filters over a layer of titanium dioxide, that a transmission density of approximately 60 from said neutral density filters was effective to prevent fogging of a diffusion transfer multicolor film unit of the type described in said US. Pat. No. 3,415,644 having a transparent support layer and an Equivalent ASA Exposure Index of approximately 75 when procesed for 1 minute in 10,000 foot candles of color-corrected light, a light intensity approximately the intensity of a noon summer sun. The transmission denaity required to protect such a film unit under the stated conditions may also be expressed in terms of the system transmission density of all the layers intermediate the silver halide layer(s) and the incident light; the system" transmission density required to protect a color film unit of the aforementioned type and photographic speed has been found to be on the order of 7.0 to 7.2. Lesser levels ofoptical transmission density would, of course, provide effective pro tection for shorter processing times, lesser light intensities and/or films having lower exposure indices. The transmission density and the indicator dye concentration necessary to provide the requisite protection from incident light may be readily determined for any photographic process by following the above-described procedure or obvious modifications thereof. It will be recognized that a particular transmission density may not be required for all portions of the spectnim. lesser density being sufficient in wavelength regions corresponding to lesser sensitivities of the particular photosensitive material.

In a particularly useful embodiment, the light-absorbing dye is highly colored at the pH of the processing composition, e.g., l3-l4. but is substantially nonabsorbing of visible light at a lower pH, e.g., less than lO-l 2. This pH reduction may be effected by an acid-reacting reagent appropriately positioned in the film unit, e.g., in a layer between the transparent support and the image-receiving layer, as described in more detail below. Such a colorchanging dye may be initially positioned in a layer of the film unit through which photoexposure is el fected if it is incorporated under conditions, e.g., pH, such that it will not absorb visible light (intended to expose the silver halide emulsions) until after application of an alkaline processing composition.

It will be understood that if the final form of the light-absorbing material at the completion of processing should be colored, it should not be present in the image-receiving layer or in any other layer where it would interfere with viewing of the transfer image through the transparent element or adversely affect the properties of said image. This result is readily obtained if the light-absorbing material is substantially colorless at the final pH of the involved layers, although suitable precautions obviously should be exercised to exclude it from the image-receiving layer if it may have an adverse effect upon the stability of the image over a prolonged period of time. If the light-absorbing dye is colored at the final pH, it may be excluded from view by mordanting it in a layer of the laminate on the opposite side of the light-reflecting layer from the layer containing the transfer image. This result may be obtained by using light-absorbing dyes which, e.g., mordant to the silver halide emulsion layer, preferably to the gelatin thereof, but not in the layers intermediate the transparent support and the light-reflecting layer.

It will be understood that the optical filter agent contemplated by this invention may be present, in whole or in part, in the light-reflecting layer when image formation is completed if it does not absorb visible light at that stage of the process. Accordingly, the optical filter agents herein contemplated may be readily distinguished from insoluble materials such as car bon black disclosed in the aforesaid patents and applications as an additive in small amounts to increase the light-protective properties of a titanium dioxide light-reflecting layer while retaining the white appearance of the titanium dioxide layer.

it will be understood that a mixture of light-absorbing materials may be used so as to obtain absorption in all critical areas of the visible and near-visible by which the silver halide emulsions, e.g., a panchromatic black-and-white silver halide emulsion or a multicolor silver halide photosensitive element, being used are exposable. Many dyes which change from colorless to colored as a function of pH, e.g., the various phthalein dyes, are known and appropriate selection may be made by one skilled in the art to meet the particular conditions of a given process and film unit. Dyes which change from colorless to colored as a function of pH are frequently referred to in the chemical and related arts as indicator dyes. If a given dye exhibits instability if stored for a period of time within a pod containing the processing composition, such a dye may be used by employing a double-compartmented rupturable pod, or two associated rupturable pods, such that the dye is stored separate from, e.g., the alkali, and the complete processing composition containing said dye is constituted at the time of use, in accordance with techniques well understood in the art.

It is also contemplated to utilize as optical filter agents dyes included in the processing composition (so as not to interfere with photoexposure) which are not colorless at the final pH of the process provided such dyes are so positioned at the end of the process as to be masked by a white reflecting layer, e.g., said optical filter agents are diffused from or through the stratum providing the white reflecting layer to a stratum containing a preferential mordant for said optical filter agent. Indeed, it is also within the scope of this invention to utilize such "behind the reflecting layer" preferential mordanting with dyes which do undergo a color change as a function of pH; this embodiment facilitates the use of dyes which clear, i.e., change from colored to colorless, more slowly than would otherwise be desirable, e.g., from the standpoint of early viewing of the transfer image without sacrificing protection of the developing photosensitive strata. The mordant for the optical filter agent should be so positioned as to retain the optical filter agent physically in a position within the film unit effective to protect the developing photosensitive strata from further exposure. Thus, this mordant is preferably located in a stratum positioned between the photosensitive strata and the reflecting layer.

As noted above, the optical filter agent may be initially positioned in a layer of the film unit, i.e., in a stratum positioned between the image-receiving layer and the photosensitive strata (e.g., in a stratum coated over either the image-receiving layer or the first photosensitive layer upon which light would be incident) in a form such that it was essentially colorless until a processing composition was applied. Thus, a pH- sensitive dye which is colorless at an acidic pH may be incorporated in a nondiffusible form in an acid state in a stratum of the film unit positioned as indicated above; application of an alkaline processing composition is effective to transform said pH-sensitive dye into its colored or light-absorbing form. This filter color generation" step should be rapid and provide light-absorbing capability effective to provide the desired light protection when the film unit is removed from the camera. The time span between application of the alkaline processing composition and exit of the film unit from the dark into the light is a function of the distance from the point at which the processing composition is applied to the exit point from the camera, the rate at which the film unit is advanced, and the rate at which the alkali is effective to render the pH-sensitive dye colored; these rates may be adjusted with respect to each other, together with the selection of the particular pH-sensitive dye or dyes, so as to provide useful light filtering for a given photographic system.

Instead of using a pH-sensitive dye in a colorless state, it is possible to use an optical filter agent precursor which is colorless as incorporated in the film unit but which becomes highly colored upon reaction with a reagent contained in the processing composition or dissolved by the processing composition from a layer of the film unit and thus made available for reaction with said optical filter agent precursor. As examples of such materials, mention may be made of chelatable organic compounds which are essentially colorless until chelated with an appropriate metal, the former being initially positioned in a layer of the film unit and the latter contained in the processing composition as a soluble metal salt capable of undergoing the desired chelation reaction.

it will therefore be seen that this invention contemplates the use of optical filter agents which are (a) initially colored and located out of the photoexposure optical path for the photosensitive material, or initially colorless if located in said optical path, (b) located in said optical path after photoexposure, and (c) may remain in the film unit after processing without interfering in the viewing of the finished image by virtue of their becoming colorless or, if colored, their final location within the film laminate being such that they are masked from view by a reflecting layer.

in those embodiments of this invention which employ a pH reduction to "discharge" the optical filter agent, e.g., to reduce the pH to a level at which the optical filtering agent is essentially colorless, this pH reduction may be effected and controlled timewise by use of a stratum containing a suitable acid. This acid stratum" or neutralizing stratum is preferably composed of a nondiffusible acid and more preferably a polymeric acid, possibly blended with one or more polymers to provide the desired concentration, distribution and availability of the acidic functional groups. Such acid strata may be referred to hereinafter for convenience as polymeric acid strata since polymeric acids are die preferred species. U.S. Pat. No. 3,362,819, issued .lan. 9, i968 to Edwin H. Land, describes and claims diffusion transfer image-receiving elements comprising a support layer possessing on one surface thereof, in sequence. a polymeric acid layer and an image-receiving layer adapted to provide a visible image upon transfer to said layer of diffusible dye image-forming substance, and most preferably include an inert timing or spacer layer intermediate the polymeric acid layer and the imagereceiving layer.

As set forth in U.S. Pat. No. 3,362,819 the polymeric acid layer comprises polymers which contain acid groups, such as carboxylic acid and sulfonic acid groups, which are capable of forming salts with alkali metals, such as sodium potassium etc., or with organic bases, particularly quaternary ammonium bases, such as tetramethyl ammonium hydroxide, or potentially acid-yielding groups, such as anhydrides or lactones, or other groups which are capable of reacting with bases to capture and retain them. In the preferred embodiments disclosed, the acid polymer contains free carboxyl groups and the transfer processing composition employed contains a large concentration of sodium and/or potassium ions. The acid polymers stated to be most useful are characterized by containing free carboxyl groups, being insoluble in water in the free acid form, and by forming water-soluble sodium and/or potassium salts. One may also employ polymers containing carboxylic acid anhydride groups, at least some of which preferably have been converted to free carboxyl groups prior to imbibition. While the most readily available polymeric acids are derivatives of cellulose or of vinyl polymers, polymeric acids from other classes of polymers may be used. As examples of specific polymeric acids set forth in said patent, mention may be made of dibasic acid half-ester derivatives or cellulose which derivatives contain free carboxyl groups, e.g., cellulose acetate hydrogen phthalate, cellulose acetate hydrogen glutarate, cellulose acetate hydrogen succinate, ethyl cellulose hydrogen succinate, ethyl cellulose acetate hydrogen succinate, cellulose acetate hydrogen succinate hydrogen phthalate; ether and ester derivatives of cellulose modified with sulfoanhydrides, e.g., with orthosulfobenaoic anhydride; polystyrene sulfonic acid; carboxymethyl cellulose; polyvinyl hydrogen phthalate; polyvinyl acetate hydrogen phthalate; polyacrylic acid; acetals of polyvinyl alcohol with carboxy or sulfo-substituted aldehydes, e.g., o-,m-, or p-benzaldehyde sulfonic acid or carboxylic acid; partial esters of ethylene/maleic anhydride copolymers; partial esters of methyl-vinyl ether/maleic anhydride copolymers; etc.

The acid polymer layer should contain at least sufficient acid groups to effect a reduction in the pH of the image layer from a pH of about 13 to 14 to a predetermined pH, e.g., l l or lower, to a pH of about to 8 within a short time. The predeterrnined pH" is a function of the processing time required to form the desired image after which point pH reduction acids in terminating further photographic processing, the time period after which light protection is not required, and the pH at which the optical filter agents color is discharged.

It is, of course, necessary that the action of the polymeric acid be so controlled as not to interfere with either development of the negative or image transfer. For this reason, the pH of the image layer preferably is kept at a level of pH 12 to l4 until the dye image has been formed after which the pH is reduced very rapidly to at least about pH 1 I, and preferably about 9 to l0. Unoxidized dye developers containing hydroquinonyl developing radicals diffuse from the negative to the positive as the sodium or other alkali salt. The diffusion rate of such dye image-forming components thus is at least partly a function of the alkali concentration, and it is usually necessary that the pH of the image layer remain on the order of [2 to 14 until transfer of the necessary quantity of dye has been accomplished. The subsequent pH reduction, in addition to its desirable effect upon image light stability, serves a highly valuable photographic function by substantially terminating further dye transfer. The processing technique thus effectively minimizes changes in image quality, e.g., color balance, as a result of the photosensitive element remaining laminated to the image-receiving layer.

In order to prevent premature pH reduction during transfer processing, as evidenced, for example, for an undesired reduction in positive image density or premature discharge of the optical filter agent, the acid groups are so distributed in the acid polymer layer that the rate of their availability to the alkali is controllable, e. g., as a function of the rate of swelling of the polymer layer which rate in turn has a direct relationship to the diffusion rate of the alkali ions. The desired distribution of the acid groups in the acid polymer layer may be effected by mixing the acid polymer with a polymer free of acid groups, or lower in concentration of acid groups, and compatible therewith, or by using only the acid polymer but selecting one having a relatively lower proportion of acid groups. These ern bodiments are illustrated, respectively, in the cited patent, by (a) a mixture of cellulose acetate and cellulose acetate hydrogen phthalate and (b) a cellulose acetate hydrogen phthalate polymer having a much lower percentage of phthalyl groups than the first-mentioned cellulose acetate hydrogen phthalate.

The layer containing the polymeric acid may contain a water-insoluble polymer, preferably a cellulose ester, which acts to control or modulate the rate at which the alkali salt of the polymer acid is formed. As examples of cellulose esters contemplated for use, mention is made of cellulose acetate, cellulose acetate butyrate, etc. The particular polymers and combinations of polymers employed in any given embodiment are, of course, selected so as to have adequate wet and dry strength and when necessary or desirable, suitable subcoats may be employed to help the various polymeric layers adhere to each other during storage and use.

The inert spacer layer, for example, an inert spacer layer comprising polyvinyl alcohol or gelatin, acts to time" control the pH reduction by the polymeric acid layer. This timing is disclosed to be a function of the rate at which the alkali diffuses through the inert spacer layer. lt was stated to have been found that the pH does not drop until the alkali has passed through the spacer layer, i.e., the pH is not reduced to any sig' nificant extent by the mere diffusion into the interlayer, but the pH drops quite rapidly once die alkali diffuses through the spacer layer.

As disclosed in said U.S. Pat. No. 3,362,819 the presence of an inert spacer layer was found to be efiective in evening out the various reaction rates over a wide range of temperatures, for example, by preventing premature pH reduction when imbibition is effected at temperatures above room temperature, for example, at to F. By providing an inert spacer layer, that application discloses that the rate at which alkali is available for capture in the polymeric acid layer becomes a function of the alkali diffusion rates.

However, as disclosed in U.S. Pat. No. 3,455,686 issued July 15, I969 in the names of Leonard C. Farney, Howard G. Rogers and Richard W. Young, preferably the aforementioned rate at which the cations of the alkaline processing composition i.e., alkali ions, are available for capture in the polymeric acid layer should be decreased with increasing transfer-processing temperatures in order to provide diffusion transfer color processes relatively independent of positive transfer image variations over an extended range of ambient temperatures.

Specifically, it is there stated to have been found that the diffusion rate of alkali through a permeable inert polymeric spacer layer increases with increased processing temperature to the extent, for example, that at relatively high transferprocessing temperatures, that is, transfer-processing temperatures above approximately 80 F a premature decrease in the pH of the transfer processing composition occurs due, at least in part, to the rapid diffusion of alkali from the dye transfer environment and its subsequent neutralization upon contact with the polymeric acid layer. This was stated to be especially true of alkali transversing an inert spacer layer possessing permeability to alkali optimized to be effective within the temperature range of optimum transfer processing. Conversely, at temperatures below the optimum transfer processing range, for example, temperatures below approximately 40 F., the last-mentioned inert spacer layer was disclosed to provide an effective diffusion barrier timewise preventing efiective traverse of the inert spacer layer by alkali having temperaturedepressed diffusion rates and to result in maintenance of the transfer processing environments high pH for such an extended time interval as to facilitate formation of transfer image stain and its resultant degradation of the positive transfer images color definition.

It is further stated in the last-mentioned U.S. Pat. No. 3.455 .686 to have been found, however that if the inert spacer layer of the print-receiving element is replaced by a spacer layer which comprises a permeable polymeric layer exhibiting permeability inversely dependent on temperature, that is, a polymeric film-forming material which exhibits increasing permeability at lower temperatures, and decreasing permeability at higher temperatures (than room temperature), to solubilized alkali-derived cations such as alkali metal and quaternary ammonium ions under conditions of increasing temperature, that the positive transfer image defects resultant from the aforementioned overextended pH maintenance and/or premature pH reduction are obviated.

As examples of polymers which were disclosed to exhibit inverse temperature-dependent permeability to alkali, mention may be made of: hydroxypropyl polyvinyl alcohol, polyvinyl methyl ether, polyethylene oxide, polyvinyl oxazolidinone, hydroxypropyl methyl cellulose, isopropyl cellulose, partial acetals of polyvinyl alcohol such as partial polyvinyl butyral, partial polyvinyl formal, partial polyvinyl acetal, partial polyvinyl propional, and the like.

The last-mentioned specified acetals of polyvinyl alcohol were stated to generally comprise saturated aliphatic hydrocarbon chains of a molecular weight of at least 1,000, preferably of about L000 to 50,000, possessing a degree of acetalation within about ID to 30 percent, to 30 percent, to 80 percent, and 10 to 40 percent, of the polyvinyl alcohols theoretical polymeric hydroxyl groups, respectively, and including mixed acetals where desired.

Where desired, a mixture of the polymers may be employed, for example, a mixture of hydroxypropyl methyl cellulose and partial polyvinyl butyral.

In lieu of using a polymeric acid layer adjacent the imagereceiving layer, as described in said US. Pat. No. 3,362,819, it is also within the scope of this invention to position such a polymeric acid layer, or a second such polymeric acid layer, adjacent the support carrying the photosensitive and imageproviding reagent strata, as described in US. Pat. No. 3,362,82! issued Jan. 9, 1968.

This invention is applicable to a wide variety of photographic processes as will be readily apparent to one skilled in the art. Dye developers are preferred image-providing substances, as indicated above, and constitute an example of initially diffusible dye image-providing substances. Other useful dye image-providing substances include initially diffusible dyes useful as image dyes per se and which couple with the oxidation product of a silver halide developing agent to provide a nondiffusible product, initially difi'usible color couplers which couple with the oxidation product of a silver halide developing agent to provide image dyes, initially nondiffusible compounds which couple with the oxidation product of a silver halide developing agent to release a diffusible dye useful as an image dye per se, and initially nondiffusible dyes which upon oxidation undergo an intramolecular ring closure to release a diffusible dye useful as an image dye per se. The final image may be formed as a result of the diffusion transfer of a soluble complex of undeveloped silver halide, in which event the image may be in silver or the transferred silver halide complex may be utilized as an intermediate in the formation of an image in dye, e.g., by using the transferred silver to catalyze the bleaching of a dye thus providing an image in tenns of unreacted dye. Alternatively, the transferred silver halide complex may be used to cause an initially nondiffusible coupling dye or ring-closing dye to undergo reaction to provide diffusible products which are removed from the image layer by diffusion to provide an image in terms of unreacted dye. A number of these imageforming systems will be discussed in more detail hereinafter.

Reference is now made to the accompanying drawings wherein a plurality of embodiments of this invention are illustrated and wherein like numbers, appearing in the various figures, refer to like components.

Referring to FIG. 1, Stages A, B and C show diagrammatic cross section, respectively, imaging, processing, and the finished print in one embodiment of this invention. For ease of understanding, FIG. 1 illustrates the formation of a monochrome image using a single dye developer. ln Stage A, there is shown a photosensitive element 30 in superposed relationship with an image-receiving element 32, with a rupturable container 16 (holding an opaque processing composition 17) so positioned as to discharge its contents between said elements upon suitable application of pressure, as by passing through a pair of pressure-applying rolls or other pressure applying means (not shown). Photosensitive element 30 comprises an opaque support 10 carrying a layer 12 of a dye developer over which has been coated a silver halide emulsion layer l4. The image-receiving element 32 comprises a transparent support 24 carrying, in turn, a polymeric acid layer 22, a spacer layer 20 and an image-receiving layer 18. Photoexposure of the silver halide emulsion layer is effected through the transparent support 24 and the layers carried thereon, i.e., the polymeric acid layer 22, the spacer layer 20 and the imagereceiving layer 18 which layers are also transparent, the film unit being so positioned within the camera that light admitted through the camera exposure or lens system is incident upon the outer or exposure surface 240 of the transparent support 24. After exposure the film unit is advanced between suitable pressure-applying members, rupturing the container 16, thereby releasing and distributing a layer l7a of the opaque processing composition and thereby forming a laminate, as il lustrated in processing Stage 8, of the photosensitive element 30 and the image-receiving element 32 with their respective support members providing the outer layers of the laminate (illustrated in Stage B). The opaque processing composition contains a film-forming polymer, a white pigment and has an initial pH at which one or more optical filter agents contained therein are colored; the optical filter (agents) is (are) selected to exhibit light absorption over at least a portion of the wavelength range of light actinic to the silver halide emulsion. As a result, ambient or environmental light within that wavelength range incident upon transparent support 24 and transmitted through said transparent support and the transparent layers carrier thereon in the direction of the exposed silver halide emulsion 14a is absorbed thereby avoiding further exposure of the photoexposed and developing silver halide emulsion 14a. in exposed and developed areas, the dye developer is oxidized as a function of the silver halide development and immobilized. Unoxidized dye developer associated with undeveloped and partially developed areas remains mobile and is transferred imagewise to the image-receiving layer 18 to provide the desired positive image therein. Permeation of the alkaline processing composition through the imagereceiving layer 18 and the spacer layer 20 to the polymeric acid layer 22 is so controlled that the process pH is maintained at a high enough level to effect the requisite development and image transfer and to retain the optical filter agent (agents) in colored form, after which pH reduction efi'ected as a result of alkali penneation into the polymeric and layer 22 is effective to reduce the pH to a level which changes the optical filter agent to a colorless form. Absorption of the water from the applied layer of the processing composition results in a solidified film composed of the film-forming polymer and the white pigment dispersed therein, thus providing reflecting layer 17b which also serves to laminate together the photosensitive element 30 and the image-receiving element 32 to provide the final laminate (Stage C). The positive transfer image in dye developer present in the image-receiving layer is viewed through the transparent support 24 and the intermediate transparent layers against the reflecting layer 17b which provides an essentially white background for the dye image and also effectively masks from view the developed silver halide emulsion Nb and dye developer immobilized therein or remaining in the dye developer layer 12.

The optical filter agent is retained within the final film unit laminate and is preferably colorless in its final form, i.e., ex-

hibiting no visible absorption to degrade the transfer image or the white background therefor provided by the reflecting layer 17b. The optical filter agent may be retained in the reflecting layer under these conditions, and it may contain a suitable "anchor" or ballast group to prevent its diffusion into adjacent layers. Alternatively, the optical filter agent may be diffusible and selectively mordanted on the silver halide emulsion side of the reflecting layer 17b, e.g., by a mordant coated on the surface of the silver halide emulsion layer 14', in this embodiment the optical filter in its final state may be colorless or colored so long as any color exhibited by it is effectively masked by the reflecting layer 17b.

The reflecting layer provided in the embodiment of this invention shown in FIG. 1 is formed by solidification of a stratum of pigmented processing composition distributed after exposure. it is also within the scope of this invention to provide a preformed pigmented layer, e.g., coated over the image-receiving layer [8, and to effect photocxposure therethrough, in accordance with the teachings of the copending application of Edwin H. Land, Ser. No. 846,44l filed July 31, I969 now US. Pat. No. 3,615,42l issued Oct. 26, 1971.

In the embodiment illustrated in FIG. 1, photo-exposure is effected through the image-receiving element. While this is a particularly useful and preferred embodiment, especially where the photosensitive element and the image-receiving element are secured together as shown in FIGS. 2, 3 and 4, it will be understood that the image-receiving element may be initially positioned out of the exposure path as illustrated in FIG. and superposed upon the photosensitive element after photoexposure.

FIG. 2 sets forth a perspective view of a particularly preferred film unit, designated 40, and each of FIGS. 3 and 4 illustrate diagrammatic cross-sectional views of film unit 40, along the stated section lines 3-3 and 4-4, during the various depicted stages in the performance of a photographic diffusion transfer process as detailed hereinafter.

Film unit 40 comprises rupturable container l6, retaining, prior to processing, aqueous processing composition 17, and photosensitive laminate 13 including, in order, dimensionally stable opaque support layer 10, preferably an actinic radiation-opaque flexible sheet material; cyan dye developer layer 45; red-sensitive silver halide emulsion layer 46; interlayer 47; magenta dye developer layer 48; green-sensitive silver halide emulsion layer 49', interlayer 50; yellow dye developer layer 51; blue-sensitive silver halide emulsion layer 52; auxiliary layer 53, which may contain an auxiliary silver halide developing agent; image-receiving layer 18; spacer layer 20; neutralizing layer 22; and dimensionally stable transparent layer 24, preferably an actinic radiation-transmissive flexible sheet material.

The structural integrity of laminate 13 may be maintained, at least in part, by the adhesive capacity exhibited between the various layers comprising the laminate at their opposed surfaces. However, the adhesive capacity exhibited at an interface intennediate image-receiving layer 18 and the silver halide emulsion layer next adjacent thereto, for example, imagereceiving layer 18 and auxiliary layer 53 as illustrated in FIGS. 3 and 4 should be less than that exhibited at the interface between the opposed surfaces of remainder of the layers forming the laminate, in order to facilitate distribution of processing solution 17 intermediate the stated image-receiving layer [8 and the silver halide emulsion layer next adjacent thereto. The laminates structural integrity may also be enhanced or provided, in whole or in part, by providing a binding member extending around, for example, the edges of laminate l3, and maintaining the layers comprising the laminate intact, except at the interface between layers 53 and 18 during distribution of processing composition 17 intermediate those layers. As illustrated in the figures, the binding member may comprise a pressure-sensitive tape 28 securing and/or maintaining the layers of laminate 13 together at its respective edges. Tape 28 will also act to maintain processing solution 17 intermediate image-receiving layer I8 and the silver halide emulsion layer next adjacent thereto, upon application of compressive pressure to pod l6 and distribution of its contents intermediate the stated layers. Under such circumstances, binder tape 28 will act to prevent leakage of fluid processing composition from the film unit's laminate during and subsequent to photographic processing.

Rupturable container 16 may be of the type shown and described in any of US. Pat. Nos. 2,5 43, l 8 l; 2,634,886; 3,653,732; 2,723,051; 3,056,492; 3,056,49]; 3,l52,5l5; and the like. in general, such containers will comprise a rectangular blank of fluid and air impervious sheet material folded longitudinally upon itself to form two walls 29 which are sealed to one another along their longitudinal and end margins to form a cavity in which processing composition l7 is retained. The longitudinal marginal seal 36 is made weaker than the end seals 31 so as to become unsealed in response to the hydraulic pressure generated within the fluid contents [7 of the con tainer by the application of compressive pressure to walls 29 of the container, e.g., by passing the film unit 40 between opposed pressure applying rollers 35.

As illustrated in FIGS. 2, 3 and 4, container 16 is fixedly positioned and extends transverse a leading edge of photosensitive laminate 13 whereby to effect unidirectional discharge of the containers contents [7 between image-receiving layer l8 and the stated layer next adjacent thereto, upon application of compressive force to container 16. Thus, container 16, as illustrated in FIG. 3, is fixedly positioned and extends transverse a leading edge of laminate l3 with its longitudinal marginal seal 36 directed toward the interface between imagereceiving layer 18 and auxiliary layer 53. As shown in FIGS. 2 and 3, container 16 is fixedly secured to laminate 13 by extension 32 of tape 28 extending over a portion of one wall 29 of the container, in combination with a separate retaining member such as illustrated retaining tape 33 extending over a portion of laminate l3s surface generally equal in area to about that covered by tape 28.

As noted, the image-receiving layer 18 may be temporarily laminated to the next adjacent layer in such a manner that these layers may be separated by the processing composition and relaminated thereby. Procedures for fabricating such prelaminated film units are set forth in the copending applications of A. .l. Bachelder and F. J. Binda, Ser. No. 744,9! 2 filed .luly l5, I968 and of Edwin H. Land, Ser. No. 804,942 filed Mar. 6, 1969.

in FIG. 6 there is shown a modification of the film unit shown in FIG, I, wherein the photosensitive element 30a includes a colorless layer 60 coated over the silver halide emulsion and containing one or more precursors of optical filter agents, e.g., pl-l-sensitive dyes coated at a pH at which they are essentially colorless and thus do not absorb light actinic to said silver halide during photoexposure. Rupture of the pod l6 distributes a pigmented alkaline processing composition effective to raise the pH of said pH-sensitive dye (dyes) and render it (them) light-absorbing, thus providing the desired opaque layer in situ. In addition, solidification of the distributed pigmented processing composition provides a reflecting layer 17b (as shown in FIG. 1) against which the transfer image formed in the image-receiving layer 18 may be viewed through the transparent support 24. In the embodiment shown in FIG. 6 it is usually not necessary to decolorize the alkali-activated optical filter agent if it is nondifi'usible to the image-receiving layer (or to a layer through which the transfer image is viewed) and the pigmented reflecting layer 17b is effective to mask it from detracting from the transfer image. Accordingly, the polymeric acid layer 22 may be omitted unless desired for its role in the photographic process, e.g., to reduce the process pH to a level at which development and transfer of image-forming components is terminated and/or to reduce the pH to a level more favorable for image stability and/or to remove from the image layer and immobilize residual reagents potentially harmful to the image.

A variation of the film unit depicted in FIG. 6 is shown in FIG. 7, wherein the colorless layer 60 containing optical filter agent precursorts) is coated over the image-receiving layer I8. In this embodiment, it is necessary that the process generated color of the filter agent be discharged to permit the transfer image to be viewed against the reflecting layer without interference. The polymeric acid layer 22 is utilized to effect this color discharge.

Suitable optical filter agents for use in embodiments such as those shown in FIGS. 6 and 7 include the pH-sensitive dyes hereinafter set forth and containing long-chain substituents or "anchors," e.g., alkyl groups containing 10 or more carbons. Suitable precautions should be exercised to avoid desensitization by the optical filter agent precursors, and one such precaution is to immobilize by suitable substituents. Alternatively, selective mordanting may be utilized to avoid undesired diffusion during preuse storage.

The use of long-chain substituents may also be desirable with optical filter agents initially present in the processing composition in order to minimize diffusion from the processing layer into one or more layers of the film unit and consequent reduction of the local concentration of the optical filter agent, thus reducing the light-absorbing effectiveness of a given quantity of the optical filter agent and possible introducing an undesired background color to the final image. Retention of the optical filter agent within the layer containing a reflecting agent, e.g., titanium dioxide, has also been found to give a multiplication" effect on apparent density, as hereinafter discussed.

A further modification of the embodiment of FIG. I is shown in FIG. 8 wherein the image-receiving element 32b includes a preformed reflecting layer 62, e.g., a layer of titanium dioxide, coated over the image-receiving layer 18, photoexposure being effected through this preformed reflecting layer. The opaque processing composition includes one or more op tical filter agents to provide an opaque layer [70, and may also contain a light-reflecting pigment which is the same or different from that in the preformed reflecting layer 62, thus reinforcing the masking capability of the reflecting layer 62. In this embodiment, as in that of FIG. 6, it may not be necessary to decoloriae the optical filter agent. Alternatively, the preformed pigmented layer 62 may be coated over the silver halide emulsion I4, in which event (as in the embodiment of FIG. 7) it is necessary to discharge the color of the optical filter agent. The provision of a preformed processing composition permeable layer, intermediate the image-receiving layer and the next adjacent silver halide layer, containing a lightreflecting pigment in a concentration which prior to photoexposure is insufficient to prevent transmission therethrough of exposing actinic radiation and which, subsequent to procesing, possesses a covering and reflecting capacity effective to mask the developed silver halide emulsion layer(s) and associated residual image-forming material is described in detail in the copending applications of Edwin H. Land, Ser. No. 846,441 filed July 3 l 1969 (now U.S. Pat. No. 3,6l5,42l issued Oct. 26, 1971 and of Sheldon A. Buckler, Ser. No. 3,646 filed Jan. l9, I970.

FIG. 9 illustrates yet another modification (of the embodiment shown in FIG. I) wherein the polymeric acid layer 22 and the spacer layer are positioned in the photosensitive element b between the opaque support It) and the dye developer layer 12. If desired, additional alkali neutralizing capability may be provided by replacing the image-receiving element 32c which does not contain a polymeric acid layer with a receiving sheet 32 which does contain such a polymeric acid layer.

In FIG. 10 there is shown an embodiment of this invention in the formation of silver transfer prints. Photosensitive element I30 comprises an opaque support 10 carrying a silver halide emulsion 14. An image-receiving element 132 comprising a transparent support 24 carrying, in turn, a polymeric acid layer 22, a spacer layer 20 and a silver receptive stratum H8, is positioned in superposed relationship with the photosensitive element 130 with a rupturable pod I6 positioned to distribute an opaque processing composition 7 between the superposed elements. In accordance with the well-known details of silver transfer processes, exposed silver halide is reduced in the photosensitive layer and a soluble, diffusible complex is formed with unexposed and underdeveloped silver halide. This soluble complex is transferred to the silverreceptive stratum 118 which preferably contains one or more silver-precipitating agents or nuclei. After the process has proceeded to the point wherein exposure of the silver halide emulsion 14 is no longer detrimental, the pH of the applied processing composition layer is reduced by the polymeric acid, in a manner analogous to that described in connection with FIG. I, and the optical filter agent which rendered the processing composition opaque is rendered colorless. The silver transfer image in the silver-receptive stratum 118 may be viewed through the transparent support 24 against a reflecting layer provided by white pigment dispersed in the layer resulting from solidification of the applied processing composition.

In the embodiments heretofore described, the desired image has been viewed against a reflecting layer, i.e., the final image is a reflection print. This invention is also applicable to the formation of images viewed by transmitted light. One such embodiment by which a developed and stabilized negative may be obtained (without concurrent formation of a transfer image) is shown in FIG. 11 wherein a first or photosensitive element 230 comprises a transparent support 24 carrying a colorless layer 60 containing an alkali-activated optical filter agent (or a preformed alkali-dischargeable dye) and a layer 14 of a silver halide emulsion. A second element 232 in superposed relationship with the photosensitive element 230 (and prelaminated thereto as discussed above, if so desired) comprises a transparent support 24 carrying a polymeric acid layer 22 and a timing layer 120. A rupturable pod 16 containing an opaque processing composition I 17a is so positioned as to distribute said processing composition between the silver halide emulsion I4 and the timing layer 120. Permeation of alkali from the processing composition activates the optical filter agent (layer 60) thus providing protection for the developing silver halide emulsion 14 from light incident upon the transparent support 24. The timing layer I20, like the spacer layer 20 in previously discussed embodiments, is of a thickness and polymeric composition effective to control the permeation of alkali therethrough to the polymeric acid layer 22, thus determining when the pl-I is reduced to a level rendering essentially colorless the optical filter agents in the processing composition and in the light barrier layer 60 behind the silver halide emulsion 14. (Since the image formed in the embodiment of FIG. II is to be viewed by transmitted light, it is not essential that the optical filter agent layers shielding the silver halide emulsion become completely colorless so long as these layers become substantially light transmitting, i.e., the optical filter agent may retain some coloration. The processing composition 1170 released by the rupture of pod I6 is free of reflecting pigment which would interfere with viewing the final image by transmitted light. (If desired, however, a reflecting pigment could be included in the processing composition 117a and the final image viewed by reflected light.) One procem by which stabilized silver negative images may be prepared and which may be used in the embodiment of FIG. 11 is described in the copending application of Edwin H. Land, Ser. No. 888,919 filed Dec. 29, I969. As disclosed therein, an element suitable for use as the polymeric acid containing element 232 in FIG. ll may be prepared by applying to the subcoated surface of a cellulose triacetate sheet an aqueous solution comprising 70 parts by weight of poly(ethylenelmaleic anhydride) commer cially available from Monsanto Chemical Co. as DX Resin Grade 840-1 l-03" and parts by weight of Elvanol 70-05" (trademark of E. I. duPont de Nemours and Co. for a lowviscosity, completely hydrolyzed polyvinyl alcohol) to provide a polymeric acid layer about 0.4 mil. thick. A timing layer about 0.15 mil. thick may then be applied comprising a graft copolymer of diacetone acrylamide and acrylamide on polyvi nyl alcohol prepared in the manner described in the copend- 

2. A diffusion transfer process as defined in claim 1 wherein said organic light-absorptive opacifying agent is a phthalein dye.
 3. A diffusion transfer process as defined in claim 1, wherein said layer containing said organic light-absorptive opacifying agent is positioned between said light-reflective layer and said transparent element, said organic light-absorptive opacifying agent absorbing substantially no visible light at the final pH of said laminate.
 4. A diffusion transfer process as defined in claim 1, wherein said layer containing said organic light-absorptive opacifying agent is positioned between said light-reflective layer and said photoexposed silver halide emulsion.
 5. A diffusion transfer process as defined in claim 1 wherein said transfer image is formed by imagewise transfer of a dye developer.
 6. A diffusion transfer process as defined in claim 1, wherein titanium dioxide is present in the processing composition applied to initiate said process, and said light-reflecting layer is formed by solidification of the applied processing composition.
 7. A diffusion transfer process comprising photoexposing a photosensitive element including a silver halide emulsion, applying a processing composition thereto to form a laminate including said photoexposed silver halide emulsion, an image-receiving layer, a transparent element and a processing composition permeable light-reflecting layer, said laminate being maintained during and after transfer image formation, developing said photoexposed silver halide emulsion and forming, as a function of said development, a diffusion transfer image in said image-receiving layer, said process being performed in the presence of an organic light-absorptive opacifying agent so constituted and so positioned in said laminate as to provide a light-absorbing barrier between said transparent element and said photoexposed silver halide emulsion during at least the early stage of said transfer image formation to prevent appreciable further exposure of said photoexposed silver halide emulsion by light passing through said transparent element, said organic light-absorptive opacifying agent being rendered ineffective as a light-absorbing barrier between said transparent element and said image-receiving layer at some stage thereafter so that said transfer image may be clearly viewed through said transparent element, said light-reflecting layer being located between said transparent element and said photoexposed silver halide emulsion and being able to mask said developed silver halide emulsion when said transfer image is viewed through said transparent element.
 8. A process as defined in claim 7 wherein said light-absorbing reagent is a dye which is colored at the pH at which said first stage of said transfer image formation is performed.
 9. A process as defined in claim 8, wherein said dye is present in the processing composition applied to initiate said process.
 10. A process as defined in claim 9, wherein said dye becomes mordanted in a layer of said laminate positioned on the opposite side of said light-reflecting layer from said image-receiving layer.
 11. A process as defined in claim 8, wherein said dye exhibits light absorption substantially outside of the visible region at a second pH which is lower than said first-mentioned pH.
 12. A process as defined in claim 11, wherein said second pH is obtained by the pH-reducing action of an acid-reacting reagent positioned within said lamInate, said pH reduction occurring after formation of said transfer image has been completed.
 13. A process as defined in claim 12, wherein said acid-reacting reagent is a polymeric acid positioned in a layer between said image-receiving layer and said transparent element.
 14. A process as defined in claim 7, wherein said light-reflecting layer comprises titanium dioxide.
 15. A process as defined in claim 14, wherein said titanium dioxide is present in the processing composition applied to initiate said process, said processing composition also including a film-forming polymer, and said light-reflecting layer is formed by solidification of the applied processing composition.
 16. A diffusion transfer process as defined in claim 7 wherein transfer image comprises a dye released for transfer as the result of a coupling reaction between an oxidized silver halide developing agent and a coupling dye,
 17. A diffusion transfer process as defined in claim 7 wherein said transfer image is formed by the diffusion transfer of unoxidized dye developer from said silver halide emulsion to said image-receiving layer.
 18. A diffusion transfer process as defined in claim 7 wherein said organic light-absorptive opacifying agent is a phthalein dye.
 19. A diffusion transfer process comprising providing a film unit including a first support and a second support, a silver halide emulsion carried on said first support and an image-receiving layer carried on said second support, said second support and the layers between it and said silver halide emulsion being transparent to radiation actinic to said silver halide emulsion; photoexposing said silver halide emulsion through said transparent second support; applying a processing composition between said image-receiving layer and said photosensitive layer, said processing composition including a light-reflecting pigment in a concentration effective to mask said photosensitive layer when said image-receiving layer is viewed through said transparent support; developing said photoexposed silver halide emulsion and forming, as a function of said development, an imagewise distribution of image-forming components which are transferred by diffusion to said image-receiving layer to provide a transfer image viewable through said transparent support without separation of said supports; said film unit further including an organic light-absorptive opacifying agent so positioned between said supports during processing and present in a concentration effective in combination with said pigment to substantially prevent further exposure of said silver halide emulsion during the performance of said transfer process in an area of light actinic to said silver halide emulsion, said opacifying agent being rendered ineffective to prevent viewing of the transfer image against a white background provided by said reflective pigment after completion of said process.
 20. A diffusion transfer process as defined in claim 19 wherein said organic light-absorptive opacifying agent is a dye which is light-absorptive at the pH of said processing composition and wherein said dye is rendered non-light-absorptive by the pH reducing action of a polymeric acid after said development has been substantially completed and formation of said transfer image has been substantially completed.
 21. A diffusion transfer process as defined in claim 19 wherein said diffusible image-forming component is a dye developer.
 22. A diffusion transfer process as defined in claim 19 wherein said diffusible image-forming component is a dye released for transfer as the result of a coupling reaction between an oxidized silver halide developing agent and a coupling dye.
 23. A diffusion transfer process as defined in claim 19 wherein said organic light-absorptive opacifying agent and said light-reflective pigment each are present in concentrations which together provide a transmission density greater than 6.0.
 24. A diffusion transfer process as defined in claim 19 whereIn said organic light-absorptive opacifying agent and said light-reflective pigment each are present in concentrations which together provide a transmission density greater than 7.0.
 25. A diffusion transfer process as defined in claim 23 wherein said organic light-absorptive opacifying agent and said light-reflective pigments are present in the same layer.
 26. A diffusion transfer process as defined in claim 25 wherein said organic light-absorptive opacifying agent is a dye which is light absorptive at the pH of said processing composition and wherein said dye is rendered non-light-absorptive by the pH-reducing action of a polymeric acid, initially present in said film unit, after said development has been substantially completed.
 27. A diffusion transfer process as defined in claim 19, wherein said first support carries a blue-sensitive silver halide emulsion, a green-sensitive silver halide emulsion, and a red-sensitive silver halide emulsion, said silver halide emulsions having associated therewith, respectively, a yellow dye developer, a magenta dye developer and a cyan dye developer, and said transfer image is a multicolor image.
 28. A process as defined in claim 27 wherein said red-sensitive silver halide emulsion, said green-sensitive silver halide emulsion and said blue-sensitive silver halide emulsion each are present as separate coplanar layers on said first support.
 29. A process as defined in claim 27 wherein said red-sensitive silver halide emulsion, said green-sensitive silver halide emulsion and said blue-sensitive silver halide emulsion are present in the form of minute elements arranged in side-by-side relationship in a photosensitive screen pattern on said first support.
 30. A diffusion transfer process as defined in claim 27, wherein said processing composition includes a mixture of organic light-absorptive opacifying agents each of which is a phthalein dye, each said phthalein dye being light-absorptive at the pH of said processing composition thereby providing absorption of light in the visible and near-visible by which said silver halide emulsions are exposable, each said phthalein dye exhibiting light absorption substantially outside of the visible region at a second and lower pH after a predetermined processing period.
 31. A diffusion transfer process as defined in claim 19, wherein said light-reflective pigment is titanium dioxide, said organic light-absorptive opacifying agent is a dye which is light-absorptive at the pH of said processing composition and is rendered non-light-absorptive by a reduction in said pH during said process, said pigment and said dye being present in concentrations effective to provide a transmission density of about 6.0.
 32. A diffusion transfer process as defined in claim 31 wherein said pH reduction is effected by a polymeric acid positioned in a layer positioned between said image-receiving layer and said transparent second support.
 33. In a photographic process wherein a photosensitive element comprising a support carrying a layer of a photosensitive material is exposed imagewise and said exposed photosensitive material is exposed imagewise and said exposed photosensitive material is treated with a processing composition distributed between said support and a second support to provide a visible image, at least one of said supports being transparent to light actinic to said photosensitive material and at least a portion of said treatment being effected in the presence of light actinic to said photosensitive layer, the improvement wherein the application of said processing composition provides a light-absorbing material effective to absorb light passing through said transparent support and actinic to said photosensitive material thereby preventing any substantial increase in the minimum density of the image in said photosensitive layer as a result of a said light being incident on said transparent support during processing of said imagewise exposed photosensitive materIal, and the light-absorbing capacity of said light-absorbing material is thereafter discharged to permit viewing through said transparent support of the visible image resulting from processing with said processing composition, said discharged light-absorbing material being substantially colorless and retained in the element containing said visible image.
 34. A photographic process comprising the steps of selectively exposing a photosensitive element comprising a layer of photosensitive material to radiation actinic thereto to provide a latent image therein, applying after said exposure a processing composition to provide an optical filter agent in a form capable of absorbing a predetermined wavelength range of said radiation actinic to said photosensitive material, and developing said latent image while exposing said photosensitive element nonselectively to incident actinic radiation within said predetermined wavelength range, said optical filter agent being present during said development in a position and quantity effective to absorb said predetermined wavelength range of incident radiation in an amount sufficient to prevent any substantial increase in the minimum density of the image obtained by said development of said latent image, said optical filter agent being retained in said element in a position and in a substantially colorless form so as to be ineffective to prevent viewing of the final image.
 35. A process as defined in claim 34 wherein said photosensitive material is silver halide.
 36. A process as defined in claim 35 wherein said silver halide is a direct positive silver halide emulsion.
 37. A process as defined in claim 34 wherein said optical filter agent is a dye which is light-absorptive at the pH of said development.
 38. A process as defined in claim 37, wherein said dye is substantially colorless at a second pH, and including the step of adjusting the pH of the stratum containing said dye to said second pH.
 39. A process as claimed in claim 34 wherein said processing composition is distributed between two strata and confined within a laminate including strata and said layer of photosensitive material.
 40. A process as defined in claim 34 wherein said final image is a diffusion transfer image.
 41. A process as defined in claim 40 wherein said transfer image is a diffusion transfer image.
 42. A process as defined in claim 41 wherein said processing composition is distributed between two strata and confined within a laminate including said strata and said layer of photosensitive material.
 43. A process as defined in claim 40 wherein said transfer image is a silver image.
 44. A process as defined in claim 40 wherein said transfer image is an additive color image.
 45. A process as defined in claim 34 wherein said final image is a negative silver image obtained by development of said latent image.
 46. A photographic film unit which comprises a plurality of sequential layers including a layer opaque to incident actinic radiation; a photosensitive silver halide layer having associated therewith image-forming material which is processing composition soluble and diffusable as a function of the point-to-point degree of silver halide layer exposure to incident actinic radiation; a layer adapted to receive solubilized image-forming material diffusing thereto; means for interposing, intermediate the silver halide layer and the reception layer, an inorganic reflecting pigment dispersion and at least one optical filter agent at a pH above the pKa of the optical filter agent in a concentration effective to provide a layer exhibiting optical transmission density > Integral 6.0 density units with respect to incident radiation actinic to the photosensitive silver halide layer and optical reflection density <* 1.0 density units with respect to incident visible radiation; and means for reducing the pH of the film unit to a pH below the pKa of the optical filter agent.
 47. A photographic film unit as defined in claim 46 wherein the means for interposing the inorganic light-reflecting pigment dispersion comprises providing a processing composition permeable layer, intermediate the silver halide layer and the reception layer, which includes an inorganic light-reflecting pigment dispersion containing at least one pH-sensitive dye at a pH below the pKa of the dye in a concentration effective upon contact with a processing composition possessing a pH above the pKa of the dye to provide a layer exhibiting optical transmission density > Integral 6.0 density units and optical reflection density <* 1.0 density units.
 48. A photographic film unit as defined in claim 46 wherein the means for interposing said inorganic light-reflecting pigment dispersion comprises means for introducing a photographic processing composition, intermediate the silver halide layer and the reception layer, which includes an inorganic light-reflecting pigment dispersion and at least one pH-sensitive dye at a pH above the pKa of the dye, to provide a layer exhibiting the optical transmission density > Integral 6.0 density units and the optical reflection density <* 1.0 density units.
 49. A photographic film unit as defined in claim 48 wherein the means for introducing the photographic processing composition comprises a rupturable container retaining the processing composition positioned extending transverse an edge of the film unit to effect, upon application of compressive pressure to the container, discharge of the container''s processing composition contents intermediate the silver halide layer and the reception layer.
 50. A photographic film unit as defined in claim 49 wherein the image-forming material is a dye image-forming material.
 51. A photographic film unit as defined in claim 50 wherein the dye image-forming material comprises a dye which is a silver halide developing agent.
 52. A photographic film unit as defined in claim 51 including, intermediate the opaque layer and the reception layer, at least two selectively sensitized silver halide emulsion layers each having a dye which dye is a silver halide developing agent of predetermined color associated therewith, each of the dyes soluble and diffusible in processing composition possessing a pH above the pKa of the pH sensitive dye as a function of the point-to-point degree of exposure of the respective emulsion associated therewith.
 53. A photographic film unit as defined in claim 52 wherein each of the selectively sensitized silver halide emulsion layers possesses predominant spectral sensitivity to separate regions of the spectrum and the dye associated with each of said silver halide emulsion layers possesses a spectral absorption range subsequent to processing substantially complementary to the predominant sensitivity image of its associated emulsion layer.
 54. A photographic film unit as defined in claim 53 wherein at least one optical filter agent exhibits, at a pH above its pKa, major spectral absorption in the spectral region within which a selectively sensitized silver halide emulsion layer possesses predominant spectral sensitivity.
 55. A photographic film unit as defined in claim 46 wherein the pH above the pKa of the filter agent is an alkaline pH.
 56. A photographic film unit as defined in claim 55 wherein the dye image-forming material comprises a dye which is a silver halide developing agent soluble and diffusible in aqueous alkaline solution at a first pH above the pKa of the filter agent and substantially nondiffusible at a second pH below the pKa of the filter agent.
 57. A photographic film unit as defined in claim 56 including at least one acid layer positioned in film unit and adapted to reduce the pH of an aqueous alkaline processing solution possessing a first pH above the pKa of the filter agent at which the dye is soluble and diffusible to a second pH below the pKa of the filter agent at which the dye is substantially nondiffusible subsequent to substantial transfer of dye to the reception layer.
 58. A photographic film unit as defined in claim 56 wherein the inorganic light-reflecting pigment titanium dioxide.
 59. A photographic film unit as defined in claim 58 wherein the optical filter agent comprises a phthalein pH-sensitive dye possessing a pKa below the first pH and above the second pH.
 60. A photographic film unit as defined in claim 59 wherein the pH-sensitive dye is substantially nondiffusible from the inorganic light-reflecting pigment dispersion.
 61. A photographic film unit as defined in claim 46 wherein said solubilized image-forming material is a dye released for transfer as the result of the reaction of an oxidized silver halide developing agent.
 62. A photographic film unit adapted to be processed by passing the unit between a pair of juxtaposed pressure-applying members and which comprises, in combination: a photosensitive element including a composition structure containing, as essential layers, a dimensionally stable opaque layer; at least two selectively sensitized silver halide emulsions layers possessing predominant spectral sensitivity to separate regions of the visible electromagnetic spectrum and a dye which is a silver halide developing agent and is soluble and diffusible, in alkaline processing composition, at a first pH associated with each of the silver halide emulsion layers and possessing a spectral absorption range subsequent to processing substantially complementary to the predominant sensitivity range of its associated emulsion layer; an alkaline solution permeable and dyeable polymeric layer; a polymeric layer possessing acid capacity effective to reduce alkaline processing composition possessing the first pH to a second pH at which the dyes are substantially nondiffusible; a dimensionally stable transparent layer; and means securing the layers in substantially fixed relationship; a rupturable container retaining an alkaline processing composition possessing the first pH and retaining substantially uniformly disposed therein titanium dioxide and optical filter agent substantially nondiffusible from the processing composition and possessing a pKa below the first pH and above the second pH wherein the filter agent exhibits spectral absorption substantially complementary to the predominant sensitivity range of the selectively sensitized silver halide emulsion layers at the first pH and the titanium dioxide and filter agent are present in a quantity sufficient, upon distribution of the alkaline processing composition possessing the first pH as a layer intermediate the dyeable polymeric layer and next adjacent selectively sensitized silver halide emulsion layer, to provide to the layer an optical transmission density > Integral 6.0 density units with respect to incident radiation actinic to the silver halide emulsion layers and an optical reflection <* 1.0 density units with respect to incident visible radiation, and said rupturable container is positioned and extends transverse an edge of the photosensitive element to effect unidirectional discharge of the container''s alkaline processing composition intermediate the dyeable polymeric layer and the selectively sensitized silver halide emulsion layer next adjacent.
 63. A photographic film unit as defined in claim 62 wherein the silver halide is present in a concentration within the image of Integral 125 to 500 mg./ft.2.
 64. A photographic film unit as defined in claim 63 wherein the titanium dioxide is distributed intermediate the dyeable polymeric layer and the silver halide emulsion layer next adjacent at a coverage within the range of Integral 1,500 to 4, 000 mg./ft.2.
 65. A photographic film unit adapted to be processed by passing said unit between a pair of juxtaposed, pressure-applying members and which comprises, in combination: a photosensitive element including a composiTe structure containing, as essential layers, in sequence, a dimensionally stable alkaline solution impermeable opaque layer; a red-sensitive silver halide emulsion layer having associated therewith cyan dye; a green-sensitive silver halide emulsion layer having associated therewith magenta dye; a blue-sensitive silver halide emulsion layer having associated therewith yellow dye, each of the cyan, magenta and yellow dyes being silver halide developing agents and being soluble and diffusible, in alkali, at a first pH; an alkaline solution permeable and dyeable polymeric layer; a polymeric layer containing sufficient acidifying capacity to effect reduction of a processing composition having the first pH to a second PH at which the dyes are substantially nondiffusible; a dimensionally stable alkaline solution impermeable transparent layer; and means securing said layers in substantially fixed relationship; and a rupturable container retaining an aqueous alkaline processing composition having the first pH and containing substantially uniformly dispersed therein titanium dioxide and at least three pH-sensitive dyes substantially nondiffusible from such processing composition and possessing a pKa below the first pH and above the second pH thereby exhibiting major spectral absorption at said first pH and minor spectral absorption at said second pH, at least one of the pH-sensitive dyes possessing predominant spectral absorption in the blue region of the electromagnetic spectrum to which the blue-sensitive emulsion is sensitive, at least one of the pH-sensitive dyes possessing predominant spectral absorption in the green region of the electromagnetic spectrum to which the green-sensitive emulsion is sensitive and at least one of the pH-sensitive dyes possessing predominant spectral absorption in the red region of the electromagnetic spectrum to which the red-sensitive emulsion is sensitive, the titanium dioxide and the pH-sensitive dyes taken together present in a quantity sufficient, upon distribution of the aqueous alkaline processing composition possessing the first pH as a layer, intermediate the dyeable polymeric layer and the blue-sensitive silver halide emulsion layer, to provide to the layer an optical transmission density > Integral 6.0 density units with respect to incident radiation actinic the silver halide emulsion layers and an optical reflection density < * 1.0 density units with respect to incident visible radiation, said container fixedly positioned and extending transverse an edge of the photosensitive element to effect unidirectional discharge of the container''s aqueous alkaline processing composition possessing the first pH intermediate the dyeable polymeric layer and the blue-sensitive silver halide emulsion layer.
 66. A photographic film unit which comprises a plurality of sequential layers including a layer transparent to incident actinic radiation; a photosensitive silver halide layer having associated therewith image-forming material which is processing composition soluble and diffusible as a function of the point-to-point degree of silver halide layer exposure to incident actinic radiation through said transparent layer; a layer adapted to receive solubilized image-forming material diffusing thereto; means for interposing, intermediate the silver halide layer and the reception layer, at least one optical filter agent in a concentration effective to provide a layer exhibiting optical transmission density with respect to incident radiation actinic to the photosensitive silver halide layer effective to shield said silver halide from actinic radiation incident upon said transparent layer after photoexposure, and means for discharging the color of said optical filter agent, subsequent to substantial diffusion of solubilized image-forming material to the layer adapted to receive image-forming material diffusing thereto, without removing said optical filter agent from said film unit.
 67. A photographic film Unit as defined in claim 66 including a layer opaque to incident actinic radiation.
 68. A photographic film unit as defined in claim 66 including means for interposing, between said silver halide layer and said receiving layer, an inorganic light-reflecting pigment dispersion.
 69. A photographic film unit as defined in claim 66 wherein said optical filter agent is a pH-sensitive dye and said means for discharging the color of said optical filter agent comprises an acid positioned in a layer of said film unit.
 70. A photographic film unit as defined in claim 69 including a polymeric layer positioned between said acid-containing layer and said optical filter agent and adapted to substantially prevent reaction of said acid with alkali for a predetermined time.
 71. A photographic film unit as defined in claim 69 wherein said acid is a polymeric acid.
 72. A photographic film unit as defined in claim 66 including means for interposing an inorganic light-reflecting white pigment dispersion between said silver halide and said receiving layer, said optical filter agent is a dye, and said means for discharging the color of said optical filter agent comprising a mordant for said optical filter agent so positioned with respect to said receiving layer as to be masked by said pigment dispersion.
 73. A photographic film unit as defined in claim 66 wherein said optical filter agent is initially positioned in a layer of said film unit in the form of a substantially colorless precursor which provides said optical filter agent by interaction with a component of said processing composition.
 74. A photographic film unit as defined in claim 73 wherein said optical filter agent is a substantially nondiffusible pH-sensitive dye initially present in said film unit at a pH below its pKa.
 75. A process for providing a photographic diffusion transfer image which comprises, in combination, the steps of: a. exposing to incident electromagnetic radiation a photographic film unit which comprises a plurality of sequential layers including a layer opaque to incident actinic radiation; a photosensitive silver halide layer having associated therewith image-forming material which is processing composition soluble and diffusible as a function of the point-to-point degree of silver halide layer exposure to incident actinic radiation; a layer adapted to receive solubilized image-forming material diffusing thereto; means for interposing, intermediate the silver halide layer and the reception layer, an inorganic reflecting pigment dispersion containing at least one optical filter agent at a pH above the pKa of the optical filter agent in a concentration effective to provide a layer exhibiting optical transmission density > Integral 6.0 density units with respect to incident radiation actinic to the photosensitive silver halide layer and optical reflection density < * 1.0 density units with respect to incident visible radiation; and means for reducing the pH of the film unit to a pH below the pKa of the optical filter agent; b. interposing the inorganic reflecting pigment dispersion intermediate the silver halide layer and the reception layer; c. contacting the photoexposed silver halide layer with a processing composition adapted to effect development of the silver halide layer; d. effecting thereby development of the photoexposed silver halide layer; e. forming thereby an imagewise distribution of mobile image-forming material as a function of the point-to-point degree of silver halide layer photoexposure; f. transferring, by diffusion, at least a portion of the imagewise distribution of mobile image-forming material to the layer adapted to receive image-forming material diffusing thereto to thereby provide an image in terms of the imagewise distribution; and g. reducing the pH of the film unit to a pH below the pKa of the optical filter agent.
 76. A process for providing a photographic diffusion transfer image as defined in claim 75 wherein the means for interposing the inorganic light-reflecting pigment dispersion comprising including within the photographic film unit, intermediate the silver halide layer and the reception layer, a preformed processing composition permeable layer which includes an inorganic light-reflecting pigment dispersion containing at least one pH-sensitive dye at a pH below the pKa of the dye and a concentration effective upon contact with a processing composition possessing a pH above the pKa of the dye to provide a layer exhibiting the optical transmission density > Integral 6.0 density units and the optical reflection density < * 1.0 density units, and including the step of contacting the pH-sensitive dye, subsequent to photoexposure of the film unit, with a processing composition possessing a pH above the pKa of the dye to provide a layer exhibiting the optical transmission density > Integral 6.0 density units and the optical reflection density < * 1.0 density units.
 77. A process for providing a photographic diffusion transfer image as defined in claim 75 wherein the processing composition adapted to effect development of the silver halide layer includes the inorganic light-reflecting pigment dispersion containing at least one pH-sensitive dye at a pH above the pKa of the dye, and including the step of interposing the processing composition, intermediate the silver halide layer and the reception layer, subsequent to photoexposure of the silver halide layer, to provide a layer exhibiting the optical transmission density > Integral 6.0 density units and the optical reflection density < * 1.0 density units.
 78. A process for providing a photographic diffusion transfer image as defined in claim 75 wherein the image-forming material is a dye image-forming material.
 79. A process for providing a photographic diffusion transfer image as defined in claim 78 wherein the dye image-forming material comprises a dye which is a silver halide developing agent.
 80. A process for providing a photographic diffusion transfer image as defined in claim 79 wherein the dye which is a silver halide developing agent is soluble and diffusible in aqueous alkaline processing composition at a first pH above the pKa of the pH-sensitive dye and substantially nondiffusible at a second pH below the pKa of the pH-sensitive dye.
 81. A process for providing a photographic diffusion transfer image in color as defined in claim 80 wherein the photographic film unit includes a layer adapted to reduce the pH of the film unit from the first pH to the second pH subsequent to substantial dye transfer image formation in the layer adapted to receive solubilized image dye diffusing thereto, and including the step of diffusing, subsequent to substantial dye transfer image formation, a sufficient portion of the ions of the alkaline processing composition to the layer adapted to reduce the pH of the film unit to thereby reduce the alkalinity of the film unit from the first pH to the second pH.
 82. A process for providing a multicolored diffusion transfer image which comprises, in combination, the steps of: a. exposing to incident actinic radiation a composite photographic film unit which comprises a plurality of sequential layers including a dimensionally stable layer opaque to incident actinic radiation; at least two selectively sensitized silver halide emulsion layers possessing predominant spectral sensitivity to separate regions of the visible electromagnetic spectrum and a dye which is a silver halide developing agent and is soluble and diffusible in aqueous alkaline processing composition, at a first pH, associated with each of the silver halide emulsion layers and possessing spectral absorption range, subsequent to processing, substantially complementary to the predominant sensitivity range of its associated silver halide emulsion layers; an alkaline solution dyeable polymEric layer; a dimensionally stable layer transparent to incident actinic radiation; at least one layer possessing neutralizing capacity effective to reduce the alkaline processing composition possessing the first pH to a second pH at which the dyes are substantially nondiffusible positioned intermediate at least one of the dimensionally stable opaque or transparent layers and next adjacent essential layer; and means of securing the layers in substantially fixed relationship; a rupturable container retaining an alkaline processing composition possessing the first pH and retaining substantially uniformly dispersed therein an inorganic light-reflecting pigment and at least one optical filter agent, substantially nondiffusible from the processing composition and possessing a pKa below the first pH and above the second pH, exhibiting spectral absorption substantially complementary to the predominant sensitivity range of the selectively sensitized silver halide emulsion layers, at the first pH, and the light-reflecting pigment and optical filter agent are present in a quantity sufficient, upon distribution of the alkaline processing composition possessing the first pH as a layer intermediate the dyeable polymeric layer and next adjacent selectively sensitized silver halide emulsion layer, to provide a layer exhibiting an optical transmission density > Integral 6.0 density units with respect to incident radiation actinic to the silver halide emulsion layers and an optical reflection density < * 1.0 density units with respect to visible radiation, and the rupturable container is positioned and extends transverse an edge of the photosensitive element to effect discharge of the container''s alkaline processing composition intermediate the dyeable polymeric layer and the selectively sensitized silver halide emulsion layer next adjacent; b. effecting discharge of the container''s alkaline processing composition intermediate the dyeable polymeric layer and the photosensitive silver halide emulsion layer next adjacent; c. effecting thereby development of each of the silver halide emulsions; d. immobilizing the dye associated with each of the silver halide emulsions as a function of the point-to-point degree of exposure thereof; e. forming thereby an imagewise distribution of mobile dye as a function of development; f. transferring, by diffusion, at least a portion of each of the imagewise distributions of mobile dye to the dyeable polymeric layer to provide thereto a dye image in terms of the imagewise distributions; g. transferring, by diffusion, subsequent to substantial dye transfer image formation, a sufficient portion of the ions of the alkaline processing composition to the neutralizing layer to thereby reduce the alkalinity of the composition from the first pH at which the dyes associated with the silver halide emulsions are soluble and diffusible and above the pKa of the pH-sensitive dye to the second pH below the pKa of the pH-sensitive dye and at which the dyes associated with the silver halide emulsions are substantially nondiffusible; and h. maintaining the composite structure intact subsequent to processing.
 83. A process for providing a photographic diffusion transfer multicolor image which comprises, in combination, the steps of: a. exposing to incident actinic radiation a photographic film unit which comprises a composite structure containing, as essential layers, in sequence, a dimensionally stable alkaline solution impermeable opaque layer; a red-sensitive silver halide emulsion layer having associated therewith cyan dye; a green-sensitive silver halide emulsion layer having associated therewith magenta dye; a blue-sensitive silver halide emulsion layer having associated therewith yellow dye, each the cyan, magenta, and yellow dyes being soluble and diffusible, in alkali, at a first pH; an alkaline solution permeable and dyeable polymeric layer; a polymeric layer containing sufficIent acidifying capacity to effect reduction of a processing composition having the first pH at which the cyan, magenta and yellow dyes are soluble and diffusible to a second pH at which the dyes are substantially nondiffusible; a dimensionally stable alkaline solution impermeable transparent layer; and means securing said layers in substantially fixed relationship; and a rupturable container retaining an aqueous alkaline processing composition having the first pH and containing substantially uniformly dispersed therein titanium dioxide and at least three pH-sensitive phthalein dyes substantially nondiffusible from said processing composition and possessing a pKa below the first pH and above the second pH, at least one of the pH-sensitive dyes possessing predominant spectral absorption in the blue region of the electromagnetic spectrum to which the blue-sensitive silver halide emulsion is sensitive, at least one of the pH-sensitive dyes possessing predominant spectral absorption in the green region of the electromagnetic spectrum to which the green-sensitive silver halide emulsion is sensitive, and at least one of the pH-sensitive dyes possessing predominant spectral absorption red region of the electromagnetic region of the spectrum to which the red-sensitive silver halide emulsion is sensitive, the titanium dioxide and the pH-sensitive dyes taken together being present in a quantity sufficient, upon distribution of the aqueous alkaline processing composition possessing the first pH as a layer intermediate the dyeable polymeric layer and the blue-sensitive silver halide emulsion layer, to provide a layer possessing an optical transmission density > Integral 6.0 density units with respect to incident radiation actinic to the silver halide emulsion layers and an optical reflection density < * 1.0 density units with respect to incident visible radiation, and the container is fixedly positioned and extends transverse a leading edge of the photosensitive element to effect upon application of compressive force unidirectional discharge of the container''s aqueous alkaline processing composition possessing the first pH intermediate the dyeable polymeric layer and blue-sensitive silver halide emulsion layer; b. applying compressive force to the rupturable container to effect unidirectional discharge of the container''s aqueous alkaline processing composition intermediate the dyeable polymeric layer and the blue-sensitive silver halide layer; c. effecting thereby development of the red, green and blue sensitive silver halide emulsion; d. immobilizing the cyan, magenta and yellow dyes as a result of development of their associated silver halide emulsion; e. forming thereby an imagewise distribution of mobile cyan, magenta and yellow dye as a function of the point-to-point degree of exposure of their associated silver halide emulsion; f. transferring, by diffusion, at least a portion of each of the imagewise distributions of mobile cyan, magenta and yellow dye to the alkaline solution permeable polymeric layer dyeable by said dyes to provide thereto a multicolor dye image; g. transferring, by diffusion, subsequent to substantial dye transfer, a sufficient portion of the ions of the aqueous alkaline processing composition to the polymeric acid layer to thereby reduce the alkalinity of the film unit from the first pH, above the pKa of the pH-sensitive dyes, at which the cyan, magenta and yellow image dyes are soluble and diffusible to a second pH, below the pKa of the pH-sensitive dyes, at which the cyan, magenta and yellow image dyes are substantially nondiffusible; and h. maintaining the composite structure intact subsequent to processing.
 84. A process for providing a photographic diffusion transfer multicolor image as defined in claim 83 wherein the titanium dioxide is distributed intermediate the dyeable polymeric layer and the blue-sensitive silver halide emulsion layer at a coverAge within the range of 1,500 to 4,000 mg./ft.2.
 85. A process for providing a photographic diffusion transfer multicolor image as defined in claim 83 wherein said optical filter agent possesses a pKa > *
 12. 86. A process for providing a photographic diffusion transfer image which comprises, in combination, the steps of: a. exposing to incident electromagnetic radiation a photographic film unit which comprises a plurality of sequential layers including a layer transparent to incident actinic radiation; a photosensitive silver halide layer having associated therewith image-forming material adapted to provide an imagewise distribution of a processing composition soluble and diffusible image-forming material as a function to the point-to-point degree of silver halide layer exposure to incident actinic radiation through such transparent layer; a layer adapted to receive solubilized image-forming material diffusing thereto; means for interposing, intermediate the silver halide layer and the reception layer, at least one optical filter agent in a concentration effective to provide a layer exhibiting optical transmission density with respect to incident radiation actinic to the photosensitive silver halide layer effective to shield said silver halide from actinic radiation incident upon said transparent layer after photoexposure; and means for discharging the color of said optical filter agent, without removing said optical filter agent from said film unit, subsequent to substantial diffusion of solubilized image-forming material to the layer adapted to receive image-forming material diffusing thereto; b. interposing said optical filter agent in a light-absorbing form intermediate said silver halide layer and said reception layer; c. contacting the photoexposed silver halide layer with a processing composition adapted to effect development of the silver halide layer; d. effecting thereby development of the photoexposed silver halide layer; e. forming thereby an imagewise distribution of diffusible image-forming material as a function of the point-to-point degree of silver halide layer photoexposure; f. transferring, by diffusion, at least a portion of the imagewise distribution of diffusible image-forming material to the layer adapted to receive image-forming material diffusing thereto to thereby provide an image in terms of the imagewise distribution; and g. discharging, subsequent to substantial transfer of said diffusible image-forming material to said reception layer, said optical filter agent.
 87. A photographic process as defined in claim 86 wherein said film unit includes a layer opaque to said incident actinic radiation.
 88. A photographic process as defined in claim 86 wherein said film unit includes a second optical filter agent positioned in a layer on the opposite side of said silver halide emulsion from said receiving layer.
 89. A photographic process as defined in claim 88 including the step of discharging said second optical filter agent subsequent to said diffusion transfer of image-forming material.
 90. A photographic process as defined in claim 86 wherein an inorganic light-reflecting white pigment dispersion is provided intermediate said silver halide layer and said receiving layer.
 91. A photographic process as defined in claim 90 wherein said pigment is included in said processing composition.
 92. A photographic process as defined in claim 86 wherein said optical filter agent is a pH-sensitive dye and the color thereof is discharged by the reaction of alkali with an acid positioned in a layer of said film unit thereby reducing, after a predetermined time, the pH of the layer containing said pH-sensitive dye to a pH below the pKa of said pH-sensitive dye.
 93. A photographic process as defined in claim 89 wherein each of said optical filter agents is a pH-sensitive dye and the color thereof is discharged by the reaction of alkali with an acid positioned in a layeR of said film unit thereby reducing, after a predetermined time, the pH of each layer containing said pH-sensitive dyes to a pH below the respective pKa of said pH-sensitive dyes.
 94. A photographic process as defined in claim 93 wherein said acid is a polymeric acid.
 95. A photographic process as defined in claim 93 wherein said film unit includes a polymeric layer positioned between said acid-containing layer and said optical filter agent and adapted to substantially prevent reaction of said acid with alkali for a predetermined time.
 96. A photographic process as defined in claim 86 wherein an inorganic light-reflecting white pigment dispersion is provided between said silver halide and said receiving layer, said optical filter agent is a dye initially present in said processing composition, and said dye is discharged by being mordanted in a stratum of said film unit so positioned as to be masked by said white pigment.
 97. A photographic process as defined in claim 86 wherein said optical filter agent is initially present as a substantially colorless precursor positioned in a layer of said film unit through which photoexposure is effected, said precursor providing said optical filter agent by interaction with a component of said processing composition.
 98. A photographic process as defined in claim 97 wherein said optical filter agent is a pH-sensitive dye initially present in said layer at a pH below its pKa.
 99. A photographic film unit comprising a plurality of superposed or superposable layers including a layer of a photosensitive silver halide and at least one outermost layer transparent to incident radiation actinic to said photosensitive silver halide; a layer adapted to contain a visible image formed as a function of development of said photosensitive silver halide and selected from the group consisting of said layer of photosensitive silver halide and a separate, superposed image-carrying layer; means adapted to interpose, intermediate said layer of photosensitive silver halide and said transparent layer and after photoexposure of said photosensitive silver halide, at least one optical filter agent in a concentration effective to provide a layer exhibiting optical transmission density, with respect to radiation actinic to said photosensitive silver halide, effective to shield said silver halide from said actinic radiation incident upon said transparent layer after photoexposure; container means releasably holding a processing composition adapted to effect development of said photosensitive silver halide after photoexposure and to provide said visible image as a function of said development; and means for discharging the color of said optical filter agent to permit viewing said visible image through said transparent layer, subsequent to substantial completion of said development and visible image formation, without removing said optical filter agent from said film unit.
 100. A photographic film unit as defined in claim 99, wherein said processing composition includes a white pigment, and said white pigment and said optical filter agent in combination are effective to provide an optical transmission density > Integral 6.0 density units with respect to incident radiation actinic to said photosensitive silver halide.
 101. A photographic film unit as defined in claim 100, wherein said optical transmission density is > Integral 7.0 density units.
 102. A photographic film unit as defined in claim 99 wherein said image-containing layer is an image-carrying layer including an image dye or an image dye intermediate adapted to be removed imagewise from said image-carrying layer as a function of said development.
 103. A photographic film unit as defined in claim 102 wherein said image-carrying layer includes a nondiffusible dye adapted to be bleached by the silver dye bleach process.
 104. A photographic film unit as defined in claim 102 wherein said image-carrying layer includes a nondiffusible dye adapted to provide a diffusible reaction product as a result of coupling with the oxidation product of a silver halide developing agent.
 105. A photographic film unit as defined in claim 102 wherein said image-carrying layer includes a nondiffusible dye adapted to provide a diffusible reaction product as a result of oxidation.
 106. A photographic film unit as defined in claim 99 wherein said optical filter agent comprises a phthalein dye.
 107. A photographic film unit as defined in claim 99 wherein said optical filter agent comprises at least two phthalein dyes.
 108. A photographic film unit as defined in claim 99 wherein said optical filter agent is substantially nondiffusible from said layer containing said optical filter agent.
 109. A photographic film unit as defined in claim 99 wherein said image-carrying layer is a silver transfer image receiving layer; and a layer containing an additive color screen positioned between said transparent outermost layer and said image-carrying layer.
 110. A photographic film unit as defined in claim 99 wherein said optical filter agent is substantially nondiffusible and is initially positioned in a layer through which photoexposure of said silver halide emulsion is effected, said layer having a pH at which said organic light-absorptive opacifying agent absorbs substantially no visible light by which said silver halide emulsion is exposable, said processing composition being effective when distributed to provide a pH at which said organic light-absorptive opacifying agent will absorb visible light by which said silver halide is exposable.
 111. A photographic film unit as defined in claim 110, wherein a second optical filter agent is included in said processing composition whereby a layer containing an optical filter agent is positioned on each side of said silver halide layer.
 112. A diffusion transfer process film unit including a first support and a second support, a silver halide emulsion carried on said first support, a dye image-providing material positioned in a layer carried on said first support, and an image-receiving layer carried on said second support, said second support and the layers between it and said silver halide emulsion being transparent to radiation actinic to said silver halide emulsion; a processing composition releasably contained in a rupturable container positioned to release said composition for distribution between said image-receiving layer and said photosensitive layer, said processing composition including a light-reflective pigment in a concentration effective to mask said photosensitive layer when said image-receiving layer is viewed through said transparent support; said dye image-providing material being adapted to provide a diffusible image-forming component as a function of said development, said film unit further including an organic light-absorptive opacifying agent adapted to be so positioned between said supports during processing and present in a concentration effective in combination with said pigment to substantially prevent further exposure of said silver halide emulsion during the performance of said transfer process in an area of light actinic to said silver halide emulsion, said opacifying agent being adapted to be rendered ineffective to prevent viewing of the transfer image against a white background provided by said reflective pigment after completion of said process.
 113. A diffusion transfer process film unit as defined in claim 112 wherein said organic light-absorptive opacifying agent is a dye which is light absorptive at the pH of said processing composition and wherein said dye is adapted to be rendered non-light-absorptive by the pH-reducing action of a polymeric acid positioned in a layer of said film unit.
 114. A diffusion transfer process film unit as defined in claim 112 wherein said diffusible image-forming component is a dye developer.
 115. A diffusion transfer process film unit as defined in claim 112 wherein said diffusible image-forminG component is a dye released for transfer as the result of a coupling reaction between an oxidized silver halide developing agent and a coupling dye.
 116. A diffusion transfer process film unit as defined in claim 112 wherein said organic light-absorptive opacifying agent is initially included in said processing composition.
 117. A diffusion transfer process film unit as defined in claim 112 wherein said organic light-absorptive opacifying agent is initially positioned in a layer through which photoexposure of said silver halide emulsion is effected, said layer having a pH at which said organic light-absorptive opacifying agent absorbs substantially no visible light by which said silver halide emulsion is exposable, said processing composition being effective when distributed to provide a pH at which said organic light-absorptive opacifying agent will absorb visible light by which said silver halide emulsion is exposable.
 118. A diffusion transfer process film unit as defined in claim 112 wherein said organic light-absorptive opacifying agent is a phthalein dye.
 119. A diffusion transfer process film unit as defined in claim 112, wherein said first support carries a blue-sensitive silver halide emulsion, a green-sensitive silver halide emulsion, and a red-sensitive silver halide emulsion, said silver halide emulsions having associated therewith, respectively, a yellow dye developer, a magenta dye developer and a cyan dye developer.
 120. A diffusion transfer process film unit as defined in claim 119, wherein said red-sensitive silver halide emulsion, said green-sensitive silver halide emulsion and said blue-sensitive silver halide emulsion each are present as separate coplanar layers on said first support.
 121. A diffusion transfer process film unit as defined in claim 119, wherein said red-sensitive silver halide emulsion, said green-sensitive silver halide emulsion and said blue-sensitive silver halide emulsion are present in the form of minute elements arranged in side-by-side relationship in a photosensitive screen pattern on said first support.
 122. A rupturable container releasably holding an aqueous alkaline processing composition for use in diffusion transfer processes including a film-forming, viscosity-providing polymer dissolved therein and an inorganic light-reflecting pigment, said composition also including a dye which absorbs light within the visible region at the pH of said aqueous alkaline composition, said dye exhibiting light absorption substantially outside of the visible region at a second pH which is lower than said first-mentioned pH.
 123. A rupturable container releasably holding an aqueous alkaline processing composition as defined in claim 122 wherein said dye is a phthalein dye.
 124. A rupturable container releasably holding an aqueous alkaline processing composition as defined in claim 122 wherein said light-reflecting pigment is titanium dioxide.
 125. A photographic film unit as defined in claim 118 wherein said layer of photosensitive material is protected from radiation actinic to said photosensitive material and incident upon the surface of said film unit opposite from said optical filter agent layer by a physically removable opaque layer.
 126. A photographic film unit as defined in claim 125 wherein said physically removable opaque layer is secured to a transparent layer by a pressure sensitive adhesive.
 127. A photographic film unit as defined in claim 66, wherein said film unit includes at least a first and a second optical filter agent, said first optical filter agent being pH sensitive and having its color discharged by a reduction in pH, and said second optical filter agent being a dye whose color is discharged by being mordanted in a layer behind a light-reflecting layer.
 128. A photographic film unit as defined in claim 66 including a development restrainer so positioned in said film unit as to become available to stop development of undeveloped silver halide after a predetermined pEriod.
 129. A photographic film unit as defined in claim 128 wherein said development restrainer is positioned in said image reception layer.
 130. A photographic film unit as defined in claim 66 including a desensitizing agent to desensitize unexposed silver halide after photoexposure and application of a processing composition.
 131. A photographic process as defined in claim 33 wherein said processing composition is providing by impregnating said processing composition into a layer carried by said second support prior to superposing said second support on said photosensitive element.
 132. An image-receiving element for use in diffusion transfer processes comprising a transparent support carrying at least a first transparent layer and a second transparent layer, said first transparent layer including a dye mordant and said second transparent layer including a substantially nondiffusible, pH-sensitive dye at a pH below its pKa whereby said pH-sensitive dye is substantially colorless.
 133. An image-receiving element as defined in claim 132 including a third transparent layer containing an acid-reacting reagent positioned between said support and said dye mordant containing layer.
 134. An image-receiving element as defined in claim 133 wherein said acid reacting reagent is a polymeric acid. 